Merge pull request
#3518 from takluyver/unused-imports...
Merge pull request
#3518 from takluyver/unused-imports
Clear up unused imports
Static analysis revealed a load of things that are imported but not used. I've tried to leave things that look like part of the API, and clear up other things.
Noticed a few test functions which had been copy-pasted without changing the name, in which case only the later one will run. I gave them separate names.
