Update .travis.yml for Qt

[kitchoi]

CI is currently failing with this error:

[EXECUTING] /home/travis/.edm/envs/edm/bin/edm run -e pyface-test-3.6-pyside2 -- coverage run -p -m unittest discover -v pyface
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.
Command '['/home/travis/.edm/envs/edm/bin/edm', 'run', '-e', 'pyface-test-3.6-pyside2', '--', 'coverage', 'run', '-p', '-m', 'unittest', 'discover', '-v', 'pyface']' returned non-zero exit status 250.

This PR attempts to fix this.

[mdickinson]

FWIW, here's the fix for this issue that worked for Envisage: enthought/envisage#287

[kitchoi]

Yep. Was trying to see whether other alternatives would work as parallel experiments. Enable does this differently too 😂

[mdickinson]

Was trying to see whether other alternatives would work as parallel experiments.

Right, I'm not fond of the Envisage solution, and would be interested in better alternatives.

[mdickinson]

It looks as though you're being bitten by this: https://github.com/enthought/buildsystem/issues/3178

[kitchoi]

It looks as though you're being bitten by this: enthought/buildsystem#3178

Looks like updating the OSX image fixed this. The libxml on the default OSX image was too old for the Qt version we are using.
The last commit has built successfully on OSX: https://travis-ci.org/github/enthought/pyface/jobs/695149507

I have been manually terminating other builds not relevant to my testing so I could focus on one thing at a time :)

[kitchoi]

The last commit has built successfully on OSX

Correction: The build actually failed, but that failure was caused by an assertion error in test. That is orthogonal to the objective of this draft PR. The entire test suite had been run.

[codecov-commenter]

Codecov Report

Merging #529 into master will decrease coverage by 0.08%.
The diff coverage is 68.04%.

@@            Coverage Diff             @@
##           master     #529      +/-   ##
==========================================
- Coverage   37.08%   36.99%   -0.09%     
==========================================
  Files         470      470              
  Lines       26027    26027              
  Branches     3961     3961              
==========================================
- Hits         9652     9629      -23     
- Misses      15948    15977      +29     
+ Partials      427      421       -6     

Impacted Files	Coverage Δ
pyface/__init__.py	82.60% <ø> (ø)
pyface/ui/qt4/init.py	62.50% <33.33%> (ø)
pyface/ui/qt4/workbench/split_tab_widget.py	12.47% <50.00%> (ø)
pyface/qt/QtNetwork.py	75.00% <60.00%> (ø)
pyface/qt/QtOpenGL.py	75.00% <60.00%> (ø)
pyface/qt/QtSvg.py	75.00% <60.00%> (ø)
pyface/qt/QtTest.py	75.00% <60.00%> (ø)
pyface/qt/QtWebKit.py	68.42% <60.00%> (ø)
pyface/qt/QtCore.py	77.77% <62.50%> (ø)
pyface/qt/QtGui.py	90.47% <66.66%> (ø)
... and 16 more

---

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[kitchoi]

History of changes for future reference:

• Linux: Tried libglu1-mesa-dev per Qt documentation: https://doc.qt.io/qt-5.14/linux.html. Did not work. The error above complaining about xcb stayed.
• Linux: Switched on QT_DEBUG_PLUGINS for debugging... then the process was more or less what happened for Fix CI failures on Linux, Windows envisage#287: You add a package, Qt complains about the next one, you add that package, Qt complains about there is still another...(repeat that N times)
• OSX: Build failed while trying to import QtWebKit:

    from PyQt5.QtWebKit import *
ImportError: dlopen(/Users/travis/.edm/envs/pyface-test-3.6-pyqt5/lib/python3.6/site-packages/PyQt5/QtWebKit.so, 2): Library not loaded: @rpath/lib/libxml2.2.dylib
  Referenced from: /Users/travis/.edm/envs/pyface-test-3.6-pyqt5/lib/libQt5WebKit.5.9.0.dylib
  Reason: Incompatible library version: libQt5WebKit.5.9.0.dylib requires version 12.0.0 or later, but libxml2.2.dylib provides version 10.0.0

• OSX: Attempted to use the brew addon on Travis to update libxml2, but ran into this issue: https://travis-ci.community/t/macos-build-fails-because-of-homebrew-bundle-unknown-command/7296/28
• OSX: Eventually updating the OSX image to use Xcode 11.5 works: It has a recent enough libxml2
• Linux: Removing libdbus seems fine. It could be due to insufficient test coverage so we might need to add this back in the future. Not sure. For now, it is not needed.
• Linux: Remove QT_DEBUG_PLUGINS. It would have been nice to keep had it not been making so much noise in between individual tests.

[kitchoi]

If it is okay, I would propose doing a squash-and-merge for this PR. Many of the commits are experimental, messy and possibly confusing when read on its own. I hope the comment above will provide the history needed for future references.

[mdickinson]

LGTM.

It seems possible that the need to specify a particular OS X image could be reverted once the buildsystem issue is solved.

[mdickinson]

I would propose doing a squash-and-merge for this PR

👍

[kitchoi]

Thank you! Squashing and merging...

It seems possible that the need to specify a particular OS X image could be reverted once the buildsystem issue is solved.

Agreed.