Unset PYTHONWARNINGS envvar before running subprocess tests.

The extra warnings in the subprocesses were causing test failures.

Closes gh-5218
Explicitly close file in get_encoding
Merge pull request #5172 from jdfreder/print-breaks

Prevent page breaks when printing notebooks via print-view.
Only pop PYTHONWARNINGS if its there.
Merge pull request #5222 from takluyver/i5218

Unset PYTHONWARNINGS envvar before running subprocess tests.
Merge pull request #5173 from jdfreder/movewidgets

Moved widget files into static/widgets/*
jshint
DEBUG

Added lots of log calls and a couple small 'fixes' (attempts)
Fixed lots of bugs

Half overhaul of notebook focus events...
Use is_focused for element kbman removal event
Added cell unfocus event canceller API
Fixed rebase problems