238 lines
8.4 KiB
Python
238 lines
8.4 KiB
Python
# Copyright 2019 Canonical Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Provide a subset of the ``python-apt`` module API.
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Data collection is done through subprocess calls to ``apt-cache`` and
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``dpkg-query`` commands.
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The main purpose for this module is to avoid dependency on the
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``python-apt`` python module.
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The indicated python module is a wrapper around the ``apt`` C++ library
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which is tightly connected to the version of the distribution it was
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shipped on. It is not developed in a backward/forward compatible manner.
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This in turn makes it incredibly hard to distribute as a wheel for a piece
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of python software that supports a span of distro releases [0][1].
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Upstream feedback like [2] does not give confidence in this ever changing,
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so with this we get rid of the dependency.
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0: https://github.com/juju-solutions/layer-basic/pull/135
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1: https://bugs.launchpad.net/charm-octavia/+bug/1824112
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2: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=845330#10
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"""
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import locale
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import os
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import subprocess
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class _container(dict):
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"""Simple container for attributes."""
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__getattr__ = dict.__getitem__
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__setattr__ = dict.__setitem__
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class Package(_container):
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"""Simple container for package attributes."""
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class Version(_container):
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"""Simple container for version attributes."""
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class Cache(object):
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"""Simulation of ``apt_pkg`` Cache object."""
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def __init__(self, progress=None):
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pass
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def __getitem__(self, package):
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"""Get information about a package from apt and dpkg databases.
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:param package: Name of package
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:type package: str
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:returns: Package object
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:rtype: object
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:raises: KeyError, subprocess.CalledProcessError
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"""
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apt_result = self._apt_cache_show([package])[package]
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apt_result['name'] = apt_result.pop('package')
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pkg = Package(apt_result)
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dpkg_result = self._dpkg_list([package]).get(package, {})
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current_ver = None
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installed_version = dpkg_result.get('version')
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if installed_version:
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current_ver = Version({'ver_str': installed_version})
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pkg.current_ver = current_ver
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pkg.architecture = dpkg_result.get('architecture')
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return pkg
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def _dpkg_list(self, packages):
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"""Get data from system dpkg database for package.
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:param packages: Packages to get data from
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:type packages: List[str]
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:returns: Structured data about installed packages, keys like
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``dpkg-query --list``
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:rtype: dict
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:raises: subprocess.CalledProcessError
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"""
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pkgs = {}
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cmd = ['dpkg-query', '--list']
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cmd.extend(packages)
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if locale.getlocale() == (None, None):
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# subprocess calls out to locale.getpreferredencoding(False) to
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# determine encoding. Workaround for Trusty where the
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# environment appears to not be set up correctly.
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locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
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try:
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output = subprocess.check_output(cmd,
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stderr=subprocess.STDOUT,
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universal_newlines=True)
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except subprocess.CalledProcessError as cp:
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# ``dpkg-query`` may return error and at the same time have
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# produced useful output, for example when asked for multiple
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# packages where some are not installed
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if cp.returncode != 1:
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raise
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output = cp.output
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headings = []
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for line in output.splitlines():
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if line.startswith('||/'):
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headings = line.split()
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headings.pop(0)
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continue
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elif (line.startswith('|') or line.startswith('+') or
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line.startswith('dpkg-query:')):
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continue
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else:
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data = line.split(None, 4)
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status = data.pop(0)
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if status != 'ii':
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continue
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pkg = {}
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pkg.update({k.lower(): v for k, v in zip(headings, data)})
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if 'name' in pkg:
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pkgs.update({pkg['name']: pkg})
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return pkgs
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def _apt_cache_show(self, packages):
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"""Get data from system apt cache for package.
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:param packages: Packages to get data from
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:type packages: List[str]
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:returns: Structured data about package, keys like
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``apt-cache show``
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:rtype: dict
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:raises: subprocess.CalledProcessError
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"""
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pkgs = {}
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cmd = ['apt-cache', 'show', '--no-all-versions']
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cmd.extend(packages)
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if locale.getlocale() == (None, None):
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# subprocess calls out to locale.getpreferredencoding(False) to
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# determine encoding. Workaround for Trusty where the
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# environment appears to not be set up correctly.
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locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
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try:
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output = subprocess.check_output(cmd,
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stderr=subprocess.STDOUT,
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universal_newlines=True)
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previous = None
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pkg = {}
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for line in output.splitlines():
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if not line:
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if 'package' in pkg:
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pkgs.update({pkg['package']: pkg})
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pkg = {}
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continue
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if line.startswith(' '):
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if previous and previous in pkg:
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pkg[previous] += os.linesep + line.lstrip()
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continue
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if ':' in line:
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kv = line.split(':', 1)
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key = kv[0].lower()
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if key == 'n':
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continue
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previous = key
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pkg.update({key: kv[1].lstrip()})
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except subprocess.CalledProcessError as cp:
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# ``apt-cache`` returns 100 if none of the packages asked for
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# exist in the apt cache.
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if cp.returncode != 100:
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raise
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return pkgs
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def init():
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"""Compability shim that does nothing."""
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pass
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def upstream_version(version):
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"""Extracts upstream version from a version string.
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Upstream reference: https://salsa.debian.org/apt-team/apt/blob/master/
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apt-pkg/deb/debversion.cc#L259
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:param version: Version string
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:type version: str
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:returns: Upstream version
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:rtype: str
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"""
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if version:
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version = version.split(':')[-1]
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version = version.split('-')[0]
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return version
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def version_compare(a, b):
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"""Compare the given versions.
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Call out to ``dpkg`` to make sure the code doing the comparison is
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compatible with what the ``apt`` library would do. Mimic the return
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values.
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Upstream reference:
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https://apt-team.pages.debian.net/python-apt/library/apt_pkg.html
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?highlight=version_compare#apt_pkg.version_compare
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:param a: version string
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:type a: str
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:param b: version string
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:type b: str
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:returns: >0 if ``a`` is greater than ``b``, 0 if a equals b,
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<0 if ``a`` is smaller than ``b``
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:rtype: int
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:raises: subprocess.CalledProcessError, RuntimeError
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"""
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for op in ('gt', 1), ('eq', 0), ('lt', -1):
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try:
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subprocess.check_call(['dpkg', '--compare-versions',
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a, op[0], b],
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stderr=subprocess.STDOUT,
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universal_newlines=True)
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return op[1]
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except subprocess.CalledProcessError as cp:
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if cp.returncode == 1:
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continue
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raise
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else:
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raise RuntimeError('Unable to compare "{}" and "{}", according to '
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'our logic they are neither greater, equal nor '
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'less than each other.')
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