Replace native test runner with pytest

setup.cfg

@@ -2,6 +2,9 @@
 # E722 do not use bare except, specify exception instead
 # F841 local variable '<variable>' is assigned to but never used
 
+[aliases]
+test=pytest
+
 [pep8]
 exclude=resources.py,vlc.py
 max-line-length = 120

setup.py

@@ -204,8 +204,9 @@ using a computer and a data projector.""",
         'PyMuPDF',
         'pyodbc',
         'pysword',
+        'pytest',
         'python-xlib; platform_system=="Linux"'
     ],
-    test_suite='tests',
+    setup_requires=['pytest-runner'],
     entry_points={'gui_scripts': ['openlp = run_openlp:start']}
 )