[issue #18730]

Closes #18720.

Patch import and initialization in SearchEngine to make testing easier.
Improve docstrings, especially to clarify the double role of 'ok' parameters.
Original patch by Phil Webster.

The latter is more ambiguous.

Related to issue #17741

already appears without #ifdef a couple lines above).

Issue #18756: os.urandom() now uses a lazily-opened persistent file descriptor, so as to avoid using many file descriptors when run in parallel from multiple threads.

Patch by A. Jesse Jiryu Davis.

Patch by A. Jesse Jiryu Davis.

The new names are hopefully more descriptive and consistent. If you feel you
don't agree with this change, *please* read issue 17741 first - there's a lot of
discussion in there.

runner were run in an environment where the process inherited an ignore
setting for SIGINT.  Restore the SIGINT handler to the desired
KeyboardInterrupt raising one during that test.

runner were run in an environment where the process inherited an ignore
setting for SIGINT.  Restore the SIGINT handler to the desired
KeyboardInterrupt raising one during that test.

sizes.

sizes.

parsing.  Added more tests for regrtest's argument parsing.

in docstrings and comments.

in docstrings and comments.