Validate Python filenames

.travis.yml

@@ -8,6 +8,7 @@ before_script:
   - black --check . || true
   - flake8 . --count --select=E9,F401,F63,F7,F82 --show-source --statistics
 script:
+  - scripts/validate_filenames.py  # no uppercase and no spaces
   - mypy --ignore-missing-imports .
   - pytest . --doctest-modules
       --ignore=data_structures/stacks/balanced_parentheses.py

scripts/validate_filenames.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python3
+
+import os
+from build_directory_md import good_filepaths
+
+filepaths = list(good_filepaths())
+assert filepaths, "good_filepaths() failed!"
+
+
+upper_files = [file for file in filepaths if file != file.lower()]
+if upper_files:
+    print(f"{len(upper_files)} files contain uppercase characters:")
+    print("\n".join(upper_files) + "\n")
+
+space_files = [file for file in filepaths if " " in file]
+if space_files:
+    print(f"{len(space_files)} files contain space characters:")
+    print("\n".join(space_files) + "\n")
+
+nodir_files = [file for file in filepaths if os.sep not in file]
+if nodir_files:
+    print(f"{len(nodir_files)} files are not in a directory:")
+    print("\n".join(nodir_files) + "\n")
+
+bad_files = len(upper_files + space_files + nodir_files)
+if bad_files:
+    import sys
+    sys.exit(bad_files)