Non existing path set in data_file causes an exception

[butla]

Reproduction:

1. Create an empty dir /var/tmp/test
2. In .coveragerc, section [run] set data_file to /var/tmp/test/inner/.coverage
3. Run any test with that.
4. FileNotFoundError is raised.

My proposition:
I'd like for that to just create the directory structure for the file. I think it can be done with os.path.dirname() and os.makedirs() here https://github.com/nedbat/coveragepy/blob/master/coverage/data.py#L495
Should that be OK?
Is there any reason not to implement that?

More context:
I'd use that when measuring coverage in an application's Docker container. Sadly, I can't just use whatever directory there is and then just issue a docker cp with a wildcard pattern to get all the .coverage.* files from the container before merging the data, because that's not implemented moby/moby#7710 I can work around that, but maybe it'd just be nice if I didn't have to.

[nedbat]

Implemented in 8271bf4

[butla]

Thanks!

[nedbat]

This was released as part of 5.0a4.