Backwards compatible alternative values possible as documented.
Done by Łukasz Langa, approved by Raymond and Fred.

Before the introduction of filename arguments to compileall it gave semi useful
messages about not being able to 'list' names that weren't valid directories.
This fix restores that behavior.  In addition to the test for this case, the
patch also adds a test for the default behavior of compileall when no arguments
are provided, and fixes a bug in one of the previously added tests.

for security reasons.  Initial patch by Ross Lagerwall.

Life is beatiful once again.

by signals on platforms using pthreads.  Patch by Reid Kleckner.

Issue 10534, difflib: tweak doc; test new SequenceMatcher instance attributes; avoid unneeded lists of SM.b2j keys and items in .__chain_b. Do not backport.