--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/planemo/lib/python3.7/site-packages/pip/_internal/distributions/source.py	Fri Jul 31 00:32:28 2020 -0400
@@ -0,0 +1,80 @@
+import logging
+
+from pip._internal.build_env import BuildEnvironment
+from pip._internal.distributions.base import AbstractDistribution
+from pip._internal.exceptions import InstallationError
+
+logger = logging.getLogger(__name__)
+
+
+class SourceDistribution(AbstractDistribution):
+    """Represents a source distribution.
+
+    The preparation step for these needs metadata for the packages to be
+    generated, either using PEP 517 or using the legacy `setup.py egg_info`.
+
+    NOTE from @pradyunsg (14 June 2019)
+    I expect SourceDistribution class will need to be split into
+    `legacy_source` (setup.py based) and `source` (PEP 517 based) when we start
+    bringing logic for preparation out of InstallRequirement into this class.
+    """
+
+    def get_pkg_resources_distribution(self):
+        return self.req.get_dist()
+
+    def prepare_distribution_metadata(self, finder, build_isolation):
+        # Prepare for building. We need to:
+        #   1. Load pyproject.toml (if it exists)
+        #   2. Set up the build environment
+
+        self.req.load_pyproject_toml()
+        should_isolate = self.req.use_pep517 and build_isolation
+
+        def _raise_conflicts(conflicting_with, conflicting_reqs):
+            raise InstallationError(
+                "Some build dependencies for %s conflict with %s: %s." % (
+                    self.req, conflicting_with, ', '.join(
+                        '%s is incompatible with %s' % (installed, wanted)
+                        for installed, wanted in sorted(conflicting))))
+
+        if should_isolate:
+            # Isolate in a BuildEnvironment and install the build-time
+            # requirements.
+            self.req.build_env = BuildEnvironment()
+            self.req.build_env.install_requirements(
+                finder, self.req.pyproject_requires, 'overlay',
+                "Installing build dependencies"
+            )
+            conflicting, missing = self.req.build_env.check_requirements(
+                self.req.requirements_to_check
+            )
+            if conflicting:
+                _raise_conflicts("PEP 517/518 supported requirements",
+                                 conflicting)
+            if missing:
+                logger.warning(
+                    "Missing build requirements in pyproject.toml for %s.",
+                    self.req,
+                )
+                logger.warning(
+                    "The project does not specify a build backend, and "
+                    "pip cannot fall back to setuptools without %s.",
+                    " and ".join(map(repr, sorted(missing)))
+                )
+            # Install any extra build dependencies that the backend requests.
+            # This must be done in a second pass, as the pyproject.toml
+            # dependencies must be installed before we can call the backend.
+            with self.req.build_env:
+                # We need to have the env active when calling the hook.
+                self.req.spin_message = "Getting requirements to build wheel"
+                reqs = self.req.pep517_backend.get_requires_for_build_wheel()
+            conflicting, missing = self.req.build_env.check_requirements(reqs)
+            if conflicting:
+                _raise_conflicts("the backend dependencies", conflicting)
+            self.req.build_env.install_requirements(
+                finder, missing, 'normal',
+                "Installing backend dependencies"
+            )
+
+        self.req.prepare_metadata()
+        self.req.assert_source_matches_version()