This can be problematic if the coverage distribution itself is not the first item on the classpath:
https://github.com/nedbat/coveragepy/blob/401471c1c51c2a99b31b0508578d04b4da03eebb/coverage/cmdline.py#L468-L470

Is there any reason this couldn't be a sys.path.insert(0, '')?

I'm happy to do the work but I just wanted to run this by you first.