reference in replacement template even if the pattern is not found in
the string.  Error message for invalid group reference now includes the
group index and the position of the reference.
Based on patch by SilentGhost.

Issue #27989: Tweak inspect.formatannotation() to improve pydoc rendering of function annotations. Ivan L. (3.5->3.6)

Issue #27989: Tweak inspect.formatannotation() to improve pydoc rendering of function annotations. Ivan L.

Patch by Piotr Szczepaniak.

* Use context manager on urllib objects to ensure that they are closed on error
* Use self.addCleanup() to cleanup resources even if a test is interrupted
  with CTRL+c

This backports a patch by Victor Stinner.

Initial patch by Hans Lawrenz.

Patch by Johannes Ebke.

Thanks to Ville Skyttä for the patch.

attributes.

new exception with setting current exception as __cause__.

_PyErr_FormatFromCause(exception, format, args...) is equivalent to Python

    raise exception(format % args) from sys.exc_info()[1]

Patch by Mariatta Wijaya.

C99 inline semantics don't work everywhere. (https://bugs.python.org/issue28092)
We don't want these to have external visibility anyway.

Patch by Vajrasky Kok.