(backport) pin pip<23.1 and setuptools<67

to allow PEP-440 non compliance.

(backported relevant parts from master branch in juju#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: juju#652

Author: ajkavanagh

charmtools/build/tactics.py

@@ -1230,6 +1230,7 @@ def __call__(self):
             utils.Process(
                 ('virtualenv', '--python', 'python3', self._venv)
             ).exit_on_error()()
+        utils.pin_setuptools_for_pep440(self._venv, env=utils.host_env())
         if self.per_layer:
             self._process_per_layer(wheelhouse)
         else:

charmtools/utils.py

@@ -633,3 +633,36 @@ def validate_display_name(entity, linter):
         linter.err('display-name: not in valid format. '
                    'Only letters, numbers, dashes, and hyphens are permitted.')
         return
+
+
+def host_env():
+    """Get environment appropriate for executing commands outside snap context.
+    :returns: Dictionary with environment variables
+    :rtype: Dict[str,str]
+    """
+    env = os.environ.copy()
+    for key in ('PREFIX', 'PYTHONHOME', 'PYTHONPATH',
+                'GIT_TEMPLATE_DIR', 'GIT_EXEC_PATH'):
+        if key in env:
+            del(env[key])
+    env['PATH'] = ':'.join([
+        element
+        for element in env['PATH'].split(':')
+        if not element.startswith('/snap/charm/')])
+    return env
+
+
+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()()

tests/test_build.py

@@ -431,14 +431,16 @@ def test_version_tactic_with_existing_version_file(self, mcall, ph, pi,
 
         self.assertEqual((bu.target_dir / 'version').text(), 'sha2')
 
+    @mock.patch("charmtools.utils.pin_setuptools_for_pep440")
     @mock.patch("charmtools.utils.sign")
     @mock.patch("charmtools.build.builder.Builder.plan_version")
     @mock.patch("charmtools.build.builder.Builder.plan_interfaces")
     @mock.patch("charmtools.build.builder.Builder.plan_hooks")
     @mock.patch("path.Path.rmtree_p")
     @mock.patch("tempfile.mkdtemp")
     @mock.patch("charmtools.utils.Process")
-    def test_wheelhouse(self, Process, mkdtemp, rmtree_p, ph, pi, pv, sign):
+    def test_wheelhouse(self, Process, mkdtemp, rmtree_p, ph, pi, pv, sign,
+                        pin_setuptools_for_pep440):
         build.tactics.WheelhouseTactic.per_layer = False
         mkdtemp.return_value = '/tmp'
         bu = build.Builder()

tests/test_utils.py

@@ -1,5 +1,6 @@
 from __future__ import print_function
 
+import unittest
 from unittest import TestCase
 from charmtools import utils
 from six import StringIO
@@ -43,3 +44,27 @@ def react(db):
         self.assertIn("Beta", output)
         self.assertIn("@when('db.ready'", output)
         self.assertIn("bar", output)
+
+    @unittest.mock.patch("os.environ")
+    def test_host_env(self, mock_environ):
+        mock_environ.copy.return_value = {
+            'PREFIX': 'fake-prefix',
+            'PYTHONHOME': 'fake-pythonhome',
+            'PYTHONPATH': 'fake-pythonpath',
+            'GIT_TEMPLATE_DIR': 'fake-git-template-dir',
+            'GIT_EXEC_PATH': 'fake-git-exec-path',
+            'SOME_OTHER_KEY': 'fake-some-other-key',
+            'PATH': '/snap/charm/current/bin:/usr/bin:'
+                    '/snap/charm/current/usr/bin:/bin',
+        }
+        self.assertDictEqual(
+            {'SOME_OTHER_KEY': 'fake-some-other-key', 'PATH': '/usr/bin:/bin'},
+            utils.host_env())
+
+    @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'})