previous 4530 number from trial included ~90 tests that trial called "passed" but actually silently skipped.
This is a successful migration of the test infrastructure from twisted.trial.unittest.TestCase to stdlib unittest.TestCase.
During the migration the automated script to update the copyright
headers accidentally got rid of some of the existing copyright lines.
Reinstate them.
Part of #9744
Removes all redundant `# -*- coding: utf-8 -*-` lines from files, as python 3 automatically reads source code as utf-8 now.
`Signed-off-by: Jonathan de Jong <jonathan@automatia.nl>`
