drop use of pkg_resources

Importing pkg_resources scans all of the installed modules for data
that won't be used. Switch to using importlib.metdata, which more
efficiently loads the metadata for a package.

Change-Id: Idd2a0d0026fef9296172c9995b428ea43a746483
Signed-off-by: Doug Hellmann <doug@doughellmann.com>

lower-constraints.txt

@@ -18,6 +18,7 @@ gitdb==0.6.4
 GitPython==1.0.1
 idna==2.5
 imagesize==0.7.1
+importlib_metadata==1.7.0
 iso8601==0.1.11
 Jinja2==2.10
 keystoneauth1==3.4.0

oslo_config/generator.py

@@ -25,15 +25,20 @@ Tool for generating a sample configuration file. See
 
 import collections
 import copy
+import json
 import logging
 import operator
 import sys
 import textwrap
 
-import json
-import pkg_resources
-import yaml
+try:
+    # For Python 3.8 and later
+    import importlib.metadata as importlib_metadata
+except ImportError:
+    # For everyone else
+    import importlib_metadata
 
+import yaml
 
 from oslo_config import cfg
 import stevedore.named  # noqa
@@ -765,7 +770,7 @@ def generate(conf, output_file=None):
 
 def main(args=None):
     """The main function of oslo-config-generator."""
-    version = pkg_resources.get_distribution('oslo.config').version
+    version = importlib_metadata.version('oslo.config')
     logging.basicConfig(level=logging.WARN)
     conf = cfg.ConfigOpts()
     register_cli_opts(conf)

oslo_config/validator.py

@@ -24,7 +24,13 @@ project then it returns those errors.
 import logging
 import sys
 
-import pkg_resources
+try:
+    # For Python 3.8 and later
+    import importlib.metadata as importlib_metadata
+except ImportError:
+    # For everyone else
+    import importlib_metadata
+
 import yaml
 
 from oslo_config import cfg
@@ -132,7 +138,7 @@ def _validate(conf):
 
 def main():
     """The main function of oslo-config-validator."""
-    version = pkg_resources.get_distribution('oslo.config').version
+    version = importlib_metadata.version('oslo.config')
     logging.basicConfig(level=logging.INFO)
     conf = cfg.ConfigOpts()
     _register_cli_opts(conf)

requirements.txt

@@ -9,3 +9,4 @@ oslo.i18n>=3.15.3 # Apache-2.0
 rfc3986>=1.2.0 # Apache-2.0
 PyYAML>=3.12 # MIT
 requests>=2.18.0 # Apache-2.0
+importlib_metadata>=1.7.0;python_version<'3.8' # Apache-2.0