Fix sphinx detection

Readthedocs has changed how it invokes sphinx. See
readthedocs/readthedocs.org#7846

Author: lpsinger

doc/conf.py

@@ -17,12 +17,18 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
+import builtins
 import configparser
 import importlib
 from pathlib import Path
 import pkg_resources
 import sys
 
+# Make it possible for our code to tell that it is running under Sphinx.
+# See https://stackoverflow.com/a/65147676/167694
+builtins.__sphinx_build__ = True
+
+
 sys.path.insert(0, str(Path(__file__).parents[1]))
 
 

gwcelery/util/sphinx.py

@@ -1,8 +1,10 @@
 """Detect if we are running under Sphinx."""
-import os
-import sys
-
 __all__ = ('SPHINX',)
 
-SPHINX = (os.path.basename(sys.argv[0]) == 'sphinx-build'
-          or 'build_sphinx' in sys.argv)
+
+try:
+    # This global builtin variable is set in doc/conf.py.
+    # See https://stackoverflow.com/a/65147676/167694
+    SPHINX = __sphinx_build__
+except NameError:
+    SPHINX = False