Fixed bug introduced by fixing a pylint error
Here first was very much intentionally set to None, as later on we
check if it is none in an 'first if first else exception' statement.
Patch by: Sverre Rabbelier
Coverage: code coverage testing for Python
Coverage.py is a Python module that measures code coverage during test execution.
It uses the code analysis tools and tracing hooks provided in the Python standard
library to determine which lines are executable, and which have been executed.
For more information, see http://nedbatchelder.com/code/modules/coverage.html