Merge pull request
#3555 from takluyver/i3547
Simplify caching of modules with %run.
Previously, we cleared and re-used a single FakeModule instance in which to run scripts, and cached copies of the modules' namespaces to prevent them from being cleared. Now, we cache one FakeModule instance per script file, clearing it and re-using it if the same script is re-run.
Closes
#3547, and fixes another test that was marked as a known failure.
