Host our own docs alone

The project tried for over 10 years to get its docs built on readthedocs.org -- but the doc files are just too big and have too much going on with Musescore etc. to have hope that they will ever be build there.

So we'll have people read the docs at music21.org/music21docs/

Author: mscuthbert

.readthedocs.yaml

@@ -12,13 +12,30 @@
 import subprocess
 
 # noinspection PyPackageRequirements
-import pytest  # pylint: disable=unused-import  # noqa
+try:
+    import pytest
+except ImportError:  # pragma: no cover
+    # fail here to get a better message than file-not-found below.
+    raise ImportError(
+        'Please install pytest -- in the music21 directory run "pip install ".[dev]"'
+    )
+
 # noinspection PyPackageRequirements
-import nbval  # pylint: disable=unused-import  # noqa
+try:
+    import nbval
+except ImportError:  # pragma: no cover
+    raise ImportError(
+        'Please install nbval -- in the music21 directory run "pip install ".[dev]"'
+    )
 
 from music21 import environment
 from music21 import common
 
+if pytest is None or nbval is None:  # pragma: no cover
+    # this will never run, but it's important to use pytest and nbval variables
+    # or some modern code linters will remove the import pytest, import nbval lines.
+    raise ImportError('Please install pytest and nbval')
+
 # pytest --nbval usersGuide_15_key.ipynb --nbval-sanitize-with ../../nbval-sanitize.cfg -q
 skip = ['installJupyter.ipynb']
 

documentation/docbuild_requirements.txt

@@ -1,4 +1,4 @@
-# Configuration file for readthedocs
+# Configuration file for docs
 # builds everything before sphinx
 
 import os