Fix pkg_resources exception handling for py312

The exception that is generated on parsing errors has changed in Python
3.12, match on the generic ValueError instead. Also switch to using
the simpler assertRaises() call instead of explicitly dealing with
exceptions.

Note that this is just a temporary workaround, we should really move
away for using pkg_resources completely, see [0] and [1].

[0] https://setuptools.pypa.io/en/latest/pkg_resources.html
[1] https://importlib-resources.readthedocs.io/en/latest/migration.html

Change-Id: I20422194f6fc6d1c4ba49da754a2c3aab99a282c
(cherry picked from commit c7d9856)

Author: osfrickler

openstack_requirements/tests/test_requirement.py

@@ -12,8 +12,6 @@
 
 import textwrap
 
-import pkg_resources
-import pkg_resources.extern.packaging.requirements as pkg_resources_reqs
 import testscenarios
 import testtools
 
@@ -107,13 +105,7 @@ class TestParseRequirementFailures(testtools.TestCase):
         ('-f', dict(line='-f http://tarballs.openstack.org/'))]
 
     def test_does_not_parse(self):
-        try:
-            requirement.parse_line(self.line)
-        except (pkg_resources.RequirementParseError,
-                pkg_resources_reqs.InvalidRequirement):
-            pass
-        else:
-            self.fail('No exception triggered')
+        self.assertRaises(ValueError, requirement.parse_line, self.line)
 
 
 class TestToContent(testtools.TestCase):
@@ -153,13 +145,8 @@ def test_urls(self):
         self.assertEqual(reqs, [(req, line)])
 
     def test_not_urls(self):
-        try:
-            list(requirement.to_reqs('file:///foo#egg=foo'))
-        except (pkg_resources.RequirementParseError,
-                pkg_resources_reqs.InvalidRequirement):
-            pass
-        else:
-            self.fail('No exception triggered')
+        self.assertRaises(
+            ValueError, list, requirement.to_reqs('file:///foo#egg=foo'))
 
     def test_multiline(self):
         content = textwrap.dedent("""\