This fixes only the case the label including both spaces and colons as
ad-hoc. There is still a bug if a label having spaces, colons and
numbers like "foo bar:baz 1234".
Note: To support the case, we have to improve the inventory format.
* rename a few test modules to make the names more consistent
* do not copy/use Sphinx from build/ (unnecessary without 2to3)
* use a temporary dir for *all* test projects, the source tree
will stay pristine that way (default is tests/build)
* speed up tests by ~3x by splitting up test projects and avoiding
rebuilds
