• Namespace packages being measured weren’t properly handled by the new code that ignores third-party packages. If the namespace package was installed, it was ignored as a third-party package. That problem (issue 1231) is now fixed.
• Packages named as “source packages” (with source, or source_pkgs, or pytest-cov’s --cov) might have been only partially measured. Their top-level statements could be marked as unexecuted, because they were imported by coverage.py before measurement began (issue 1232). This is now fixed, but the package will be imported twice, once by coverage.py, then again by your test suite. This could cause problems if importing the package has side effects.
• The CoverageData.contexts_by_lineno() method was documented to return a dict, but was returning a defaultdict. Now it returns a plain dict. It also no longer returns negative numbered keys.