[doc] Fix mermaid sphinx incompatibility

Author: IceflowRE

documentation/requirements.txt

@@ -1,4 +1,4 @@
-sphinx>=3.0.1
+sphinx>=4.0.0
 sphinx_rtd_theme>=0.4.3
 exhale>=0.2.3
 sphinxcontrib-mermaid>=0.4.0

documentation/source/conf.py

@@ -6,6 +6,15 @@
 sys.path.insert(0, str(Path('../../').resolve()))
 sys.path.insert(0, str(Path('../').resolve()))
 
+# TODO(#394): Remove this when this PR is merged:
+# https://github.com/mgaitan/sphinxcontrib-mermaid/pull/71
+# Needed for sphinxcontrib-mermaid compatibility with sphinx 4.0.0.
+import sphinx
+if sphinx.version_info[0] >= 4:
+    import errno
+    import sphinx.util.osutil
+    sphinx.util.osutil.ENOENT = errno.ENOENT
+
 from helper import generate_radar
 # generate additional source stuff
 generate_radar.generate(Path("./auto-generated/"))