When running tests from subfolders, import by "full dotted path" rather
than just module name, removing the need to add the test parent folder to
`sys.path`.
This matches CPython more closely, which places `abspath(top)` at the start
of `sys.path` but doesn't include the test file parent dir at all.
It fixes issues where projects may include a `test_xxx.py` file in their
distribution which would (prior to this change) be unintentionally found by
unittest-discover.
Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>
Andrew Leech