Add imports check to travis build

This will compile a list of Python files in OmeroWeb and try to import
them to discover if any file has imports that do not work.

flake8 does not detect non-working imports.
Move import check after build step
Add pythonpath for django requirement
Merge branch 'develop' into travis-omeroweb-imports-check

Conflicts:
	components/tools/travis-build
Install pytest via pip for import check
Log imports being checked to output
Convert SessionControl._parse_conn into a static method
Add unit tests for static SessionsControl._parse_conn() method
Use group naming for clarity in _parse_conn and add docstring
Extend unit tests to cover empty string input
Add tests for connection string parsing with wild users and bad ports

- Increase stringency of regular expression to match up to 5 digits for ports
- Test connection string with user containing both : and @ characters
- Add test with invalid port and check the port is parsed with the server name
Merge pull request #2350 from knabar/travis-omeroweb-imports-check

Travis check for Python imports in OmeroWeb
Merge pull request #2374 from snoopycrimecop/merge/develop/submodules

Update develop submodules (periodic merge)
Merge pull request #2388 from sbesson/rebased/develop/parse_conn_tests

Add unit tests for CLI connection string parser (rebased onto develop)
Update develop submodules

Repository: openmicroscopy/openmicroscopy
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Repository: openmicroscopy/bioformats
Updating f247b30..fd9b562
Merged PRs (fast-forward):
  # PR 1073 rleigh-dundee 'docs: Delegate all sphinx Makefile targets to ant'

Repository: ome/scripts
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Repository: openmicroscopy/ome-documentation
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