tests/sitecustomize.py

import-checker: fix names of dynamically loaded modules

The import checker found standard library modules such as
lib-dynload/zlibmodule.so but saw that as a 'zlibmodule' module, not as the
'zlib' module.

Debian ships Python with most modules built-in and this incorrect handling of
dynamic modules did thus not cause problems on that platform.

Fedora ships Python with as many modules as possible loaded dynamically. That
made the import checker tests fail with incorrect classification of the
following modules: array fcntl grp itertools time zlib.

This change makes test-module-imports.t pass on Fedora.

try:
    import coverage
    getattr(coverage, 'process_startup', lambda: None)()
except ImportError:
    pass