py-coverage: updated to 4.5.1

Version 4.5.1:

- Now that 4.5 properly separated the [run] omit and [report] omit
  settings, an old bug has become apparent.  If you specified a package name
  for [run] source, then omit patterns weren't matched inside that package.
  This bug (issue 638_) is now fixed.

- On Python 3.7, reporting about a decorated function with no body other than a
  docstring would crash coverage.py with an IndexError (issue 640_).  This is
  now fixed.

- Configurer plugins are now reported in the output of --debug=sys.

(adam)