Python: add comment about namespace packages

Author: yoff

python/ql/lib/semmle/python/Module.qll

@@ -195,6 +195,14 @@ private predicate isPotentialPackage(Folder f) {
 }
 
 private string moduleNameFromBase(Container file) {
+  // We used to also require `isPotentialPackage(f)` to hold in this case,
+  // but we saw modules not getting resolved because their folder did not
+  // contain an `__init__.py` file.
+  //
+  // This makes the folder not be a package but a namespace package instead.
+  //
+  // It is possible that we can keep the requirement here, but relax
+  // `isPotentialPackage` itself to allow for namespace packages.
   result = file.getBaseName()
   or
   file instanceof File and result = file.getStem()