Pin pip<23.1 and setuptools<67 to allow PEP-440 non compliance (#653)

PEP-440 is more strict about requirement lines.  As an example:

    pytz>dev

is non-compliant, but is in 5.2.4 of kombu's requirements.  This breaks
building wheelhouses from source (such as the octavia charm).  This
patch pins pip and setuptools to the latest versions that will defintely
still allow PEP-440 non-compliant packages to install.

The option --upgrade-buildvenv-core-deps can be used to override this
and will install the latest versions of pip and setuptools available.

Fixes-Bug: #652

charmtools/build/tactics.py

@@ -1252,6 +1252,8 @@ def __call__(self):
             ).exit_on_error()()
         if self.upgrade_deps:
             utils.upgrade_venv_core_packages(self._venv, env=self._get_env())
+        else:
+            utils.pin_setuptools_for_pep440(self._venv, env=self._get_env())
         log.debug(
             'Packages in buildvenv:\n{}'
             .format(

charmtools/utils.py

@@ -670,6 +670,24 @@ def upgrade_venv_core_packages(venv_dir, env=None):
             env=env).exit_on_error()()
 
 
+def pin_setuptools_for_pep440(venv_dir, env=None):
+    """Pin setuptools so that pep440 non-compliant packages can be installed.
+
+    Also pins pip as it's a combination that definitely works.
+
+    :param venv_dir: Full path to virtualenv in which packages will be upgraded
+    :type venv_dir: str
+    :param env: Environment to use when executing command
+    :type env: Optional[Dict[str,str]]
+    :returns: This function is called for its side effect
+    """
+    log.debug('Pinning setuptools < 67 for pep440 non compliant packages "{}"'
+              .format(venv_dir))
+    Process((os.path.join(venv_dir, 'bin/pip'),
+             'install', '-U', 'pip<23.1', 'setuptools<67'),
+            env=env).exit_on_error()()
+
+
 def get_venv_package_list(venv_dir, env=None):
     """Get list of packages and their version in virtualenv.
 

tests/test_utils.py

@@ -68,6 +68,14 @@ def test_upgrade_venv_core_packages(self, mock_Process):
             ('/some/dir/bin/pip', 'install', '-U', 'pip', 'setuptools'),
             env={'some': 'envvar'})
 
+    @unittest.mock.patch.object(utils, "Process")
+    def test_pin_setuptools_for_pep440(self, mock_Process):
+        utils.pin_setuptools_for_pep440('/some/dir', env={'some': 'envvar'})
+        mock_Process.assert_called_once_with(
+            ('/some/dir/bin/pip', 'install', '-U', 'pip<23.1',
+             'setuptools<67'),
+            env={'some': 'envvar'})
+
     @unittest.mock.patch("sys.exit")
     @unittest.mock.patch.object(utils, "Process")
     def test_get_venv_package_list(self, mock_Process, mock_sys_exit):