Remove logic for Python <= 2.6

... because that old version is no longer supported.

Also the check_python_version method is removed by this change, because
the required python version is now enforced by setup.cfg.

Change-Id: Ie9c91adcb81a1a5dbca2587b6592a58d4cc91e4a

tools/colorizer.py

@@ -322,11 +322,7 @@ class SubunitTestResult(testtools.TestResult):
 
 test = subunit.ProtocolTestCase(sys.stdin, passthrough=None)
 
-if sys.version_info[0:2] <= (2, 6):
-    runner = unittest.TextTestRunner(verbosity=2)
-else:
-    runner = unittest.TextTestRunner(
-        verbosity=2, resultclass=SubunitTestResult)
+runner = unittest.TextTestRunner(verbosity=2, resultclass=SubunitTestResult)
 
 if runner.run(test).wasSuccessful():
     exit_code = 0

tools/install_venv.py

@@ -59,7 +59,6 @@ def main(argv):
     install = install_venv.InstallVenv(root, venv, pip_requires, test_requires,
                                        py_version, project)
     options = install.parse_args(argv)
-    install.check_python_version()
     install.check_dependencies()
     install.create_virtualenv(no_site_packages=options.no_site_packages)
     install.install_dependencies()

tools/install_venv_common.py

@@ -16,9 +16,6 @@
 """Provides methods needed by installation script for OpenStack development
 virtual environments.
 
-Since this script is used to bootstrap a virtualenv from the system's Python
-environment, it should be kept strictly compatible with Python 2.6.
-
 Synced in from openstack-common
 """
 
@@ -44,10 +41,6 @@ class InstallVenv(object):
         print(message % args, file=sys.stderr)
         sys.exit(1)
 
-    def check_python_version(self):
-        if sys.version_info < (2, 6):
-            self.die("Need Python Version >= 2.6")
-
     def run_command_with_code(self, cmd, redirect_output=True,
                               check_exit_code=True):
         """Runs a command in an out-of-process shell.