Support entry point patching on setuptools < 12

In patch 789888 we began relying on EntryPoint.resolve(), which only
exists in setuptools >= 12, breaking support for setuptools < 12.  This
includes the default virtualenv installations from may LTS distributions.
As ep.load with arguments is deprecated we will attempt to use
ep.resolve if it exists and fall back to ep.load(false) if it does not.
setuptools 11 is the odd release out, as this was when load with
arguments was deprecated, suggesting the use of ep._load.  We will
continue to use ep.load(False) here.

Change-Id: I272f76fef7e447378697a3980372191f4ffe1a2f

pbr/tests/test_integration.py

@@ -184,9 +184,12 @@ class TestInstallWithoutPbr(base.BaseTestCase):
 class TestMarkersPip(base.BaseTestCase):
 
     scenarios = [
-        ('pip-1.5', {'version': 'pip>=1.5,<1.6'}),
-        ('pip-6.0', {'version': 'pip>=6.0,<6.1'}),
-        ('pip-latest', {'version': 'pip'}),
+        ('pip-1.5', {'modules': ['pip>=1.5,<1.6']}),
+        ('pip-6.0', {'modules': ['pip>=6.0,<6.1']}),
+        ('pip-latest', {'modules': ['pip']}),
+        ('setuptools-EL7', {'modules': ['pip==1.4.1', 'setuptools==0.9.8']}),
+        ('setuptools-Trusty', {'modules': ['pip==1.5', 'setuptools==2.2']}),
+        ('setuptools-minimum', {'modules': ['pip==1.5', 'setuptools==0.7.2']}),
     ]
 
     @testtools.skipUnless(
@@ -208,14 +211,15 @@ class TestMarkersPip(base.BaseTestCase):
         venv = self.useFixture(Venv('markers'))
         bin_python = venv.python
         os.mkdir(repo_dir)
+        for module in self.modules:
+            self._run_cmd(
+                bin_python,
+                ['-m', 'pip', 'install', '--upgrade', module],
+                cwd=venv.path, allow_fail=False)
         for pkg in pkg_dirs:
             self._run_cmd(
                 bin_python, ['setup.py', 'sdist', '-d', repo_dir],
                 cwd=pkg_dirs[pkg], allow_fail=False)
-        self._run_cmd(
-            bin_python,
-            ['-m', 'pip', 'install', '--upgrade', self.version],
-            cwd=venv.path, allow_fail=False)
         self._run_cmd(
             bin_python,
             ['-m', 'pip', 'install', '--no-index', '-f', repo_dir,
@@ -224,3 +228,29 @@ class TestMarkersPip(base.BaseTestCase):
         self.assertIn('pkg-b', self._run_cmd(
             bin_python, ['-m', 'pip', 'freeze'], cwd=venv.path,
             allow_fail=False)[0])
+
+
+class TestLTSSupport(base.BaseTestCase):
+
+    # These versions come from the versions installed from the 'virtualenv'
+    # command from the 'python-virtualenv' package.
+    scenarios = [
+        ('EL7', {'modules': ['pip==1.4.1', 'setuptools==0.9.8']}),  # And EPEL6
+        ('Trusty', {'modules': ['pip==1.5', 'setuptools==2.2']}),
+        ('Jessie', {'modules': ['pip==1.5.6', 'setuptools==5.5.1']}),
+        # Wheezy has pip1.1, which cannot be called with '-m pip'
+        # So we'll use a different version of pip here.
+        ('WheezyPrecise', {'modules': ['pip==1.4.1', 'setuptools==0.6c11']})
+    ]
+
+    @testtools.skipUnless(
+        os.environ.get('PBR_INTEGRATION', None) == '1',
+        'integration tests not enabled')
+    def test_lts_venv_default_versions(self):
+        venv = self.useFixture(Venv('setuptools', modules=self.modules))
+        bin_python = venv.python
+        pbr = 'file://%s#egg=pbr' % PBR_ROOT
+        # Installing PBR is a reasonable indication that we are not broken on
+        # this particular combination of setuptools and pip.
+        self._run_cmd(bin_python, ['-m', 'pip', 'install', pbr],
+                      cwd=venv.path, allow_fail=False)

pbr/util.py

@@ -556,7 +556,15 @@ def wrap_commands(kwargs):
     # with this here.
     for ep in pkg_resources.iter_entry_points('distutils.commands'):
         if ep.name not in dist.cmdclass:
-            cmdclass = ep.resolve()
+            if hasattr(ep, 'resolve'):
+                cmdclass = ep.resolve()
+            else:
+                # Old setuptools does not have ep.resolve, and load with
+                # arguments is depricated in 11+.  Use resolve, 12+, if we
+                # can, otherwise fall back to load.
+                # Setuptools 11 will throw a deprication warning, as it
+                # uses _load instead of resolve.
+                cmdclass = ep.load(False)
             dist.cmdclass[ep.name] = cmdclass
 
     for cmd, _ in dist.get_command_list():