Enabling Python Generators

Summary

This change enables the ability to choose to use the Python module dependency generator for packages that provide Python Egg/Wheel metadata.

Owner

Name: Igor Gnatenko, Neal Gompa
Email: ignatenkobrain@fedoraproject.org, ngompa13@gmail.com
Release notes owner:

Current status

Targeted release: Fedora 28
Last updated: 2018-01-19
Tracker bug: <will be assigned by the Wrangler>

Detailed Description

... For F28 this is opt-in, in F29 we plan to propose to make this opt-out.

Benefit to Fedora

Packagers do not need to specify runtime dependencies manually anymore
No more errors in runtime due to missing dependencies (see example below)

Packager of python-fasteners forgot to add Requires: python3-monotonic >= 0.1 so when anyone does "import fasteners", it fails with traceback:

Traceback (most recent call last):

 File "/builddir/build/BUILD/jenkins-job-builder-2.0.0/tests/yamlparser/test_yamlparser.py", line 42, in test_incorrect_template_dimensions
   reg = registry.ModuleRegistry(config)
 File "/builddir/build/BUILD/jenkins-job-builder-2.0.0/jenkins_jobs/registry.py", line 50, in __init__
   Mod = entrypoint.load()
 File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2407, in load
   self.require(*args, **kwargs)
 File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2430, in require
   items = working_set.resolve(reqs, env, installer, extras=self.extras)
 File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 870, in resolve
   raise DistributionNotFound(req, requirers)

pkg_resources.DistributionNotFound: The 'monotonic>=0.1' distribution was not found and is required by fasteners

With automatic dependency management this should never happen.

Scope

Proposal owners:

Other developers: N/A (not a System Wide Change)

Release engineering: #Releng issue number (a check of an impact with Release Engineering is needed)
- List of deliverables: N/A (not a System Wide Change)

Policies and guidelines: N/A (not a System Wide Change)

Packaging:Python Guidelines need to reference how to turn on the feature (simple variable override).

Trademark approval: N/A (not needed for this Change)

Upgrade/compatibility impact

Some new dependencies might be automatically added, but this is rather good because it fixes real bugs.