This is quite invasive. Wouldn't syntax errors cause the tests to not run at all?

utACK 7777994, this looks like good cleanup to me.

@laanwj Indeed this is touching 129 lines, but all of it should be uncontroversial:

• Python will silently ignore trailing semicolons and I don't feel strong about this change. Still, I think we should not promote such usage.
• Excessive imports won't hurt performance too much but they fuzz the code, imo.
• Finally, python will only complain about syntax errors on runtime. Luckily all of the syntax errors behave like they are not there: You can do raise AssertionFailure("Failed to mine a version=4 blocks") to raise a NameError: name 'AssertionFailure' is not defined which makes travis fail as well but I think raise AssertionError("Failed to mine a version=4 blocks") is much clearer.

Concept ACK

@MarcoFalke Thanks for the explanation, makes sense.
utACK

Ran this through the extended test suite, no issues.