flake8 cleanup of some test files
Minor typo fixes
Minor refactoring of BFPPB for testing

In order to be able to intercept (and block) certain
methods of BFPPB for concurrency testing methods have
been changed to `protected` and an `init()` method has
been introduced to allow a ctor with less logic.
Passing test with intermediate fix

The change (basically to not lock on read) makes
this test pass where before it was failing (when
`Thread.sleep()` was artificially introduced for
calls to releaseLock.

It's unknown if this will be sufficiently safe
going forward.
Extract Django when it's missing or is the wrong version
Add missing delete task
merge dev_4_4 -D org -I include -E exclude: PR 1690 (Webfigure TEMP)
merge dev_4_4 -D org -I include -E exclude: PR 1799 (Fix intermittent test failures in OmeroPy-integration-stable.)
merge dev_4_4 -D org -I include -E exclude: PR 1805 (Upgrade ICE jars to version 3.5.1 (4.4))
merge dev_4_4 -D org -I include -E exclude: PR 1819 (Update dev_4_4 submodules)
merge dev_4_4 -D org -I include -E exclude: PR 1823 (Initialize table before file chooser.)
merge dev_4_4 -D org -I include -E exclude: PR 1827 (ldap discover username/password fix, paging and dn check (rebased onto dev_4_4))
merge dev_4_4 -D org -I include -E exclude: PR 1831 (fix #10581: getTile byte-ordering issue (rebased onto dev_4_4))
merge dev_4_4 -D org -I include -E exclude: PR 1833 (Add annotation ID to FileAnnotation tooltip in OMERO.insight (rebased onto dev_4_4))
merge dev_4_4 -D org -I include -E exclude: PR 1834 (#11723 adding FORCE_SCRIPT_NAME to the settings.py (rebased onto dev_4_4))
merge dev_4_4 -D org -I include -E exclude: PR 1835 (Simplify Travis environments (rebased onto dev_4_4))
merge dev_4_4 -D org -I include -E exclude: PR 1839 (Error handling of tile image loading in PanoJS See #11709)
merge dev_4_4 -D org -I include -E exclude: PR 1843 (Disable chgrp event logs)
merge dev_4_4 -D org -I include -E exclude: PR 1848 (11709 tile access)
merge dev_4_4 -D org -I include -E exclude: PR 1850 (dev_4_4: Extract Django when it's missing or is the wrong version)