test infra: clear file-charged issues on rerun of file

test infra: clear file-charged issues on rerun of file

This change addresses the corner case bug in the test
infrastructure where a test file times out *outside*
of any running test method.  In those cases, the issue
was charged to the file, not to a test method within
the file.  When that file is re-run successfully,
none of the test-method-level successes would clear
the file-level issue.

This change fixes that: for all test files that are
getting rerun (whether by being marked flaky or
via the --rerun-all-issues flag), file-level test
issues are searched for in each of those files.  Each
file-level issue found in the rerun file list then
gets cleared.

A test of this feature is added to issue_verification,
using the technique there of moving the *.py.park file
to *.py to do an end-to-end validation.

This change also adds a .gitignore entry for pyenv
project-level files and fixes up a few minor pep8
formatting violations in files I touched.

Fixes:
llvm.org/pr27423

llvm-svn: 282990