Patch by Sandro Tosi.

Patch by Sandro Tosi.  The main purpose of this option is to allow
an alternate set of tests files to be used when running tests
of the regrtest tool itself.

Algorithm and initial patch by Michael Henry.

Move __name__ back out of the template; the responsibility
for setting __name__ lies with the caller (which knows
something about the new namespace), not with the class
definition (which doesn't know about the namespace it is
being built in).

paths.

__import__ does a little trick when importing from bytecode by
back-patching the co_filename paths to point to the file location
where the code object was loaded from, *not* where the code object was
originally created. This allows co_filename to point to a valid path.
Problem is that co_filename is immutable from Python, so a private
function -- imp._fix_co_filename() -- had to be introduced in order to
get things working properly. Originally the plan was to add a file
argument to marshal.loads(), but that failed as the algorithm used by
__import__ is not fully recursive as one might expect, so to be fully
backwards-compatible the code used by __import__ needed to be exposed.

This closes issue #6811 by taking a different approach than outlined
in the issue.

This makes it obvious that an import failed because of some extraneous
whitespace (e.g., a newline).

This is a partial fix for issue #8754.

appropriate number of parallel workers.

parallel (thanks Michael for pointing this).