Resolve issues on Windows by escaping path separators first

Author: shreve

nbgrader/coursedir.py

@@ -438,13 +438,13 @@ def find_notebooks(
             for key, value in kwargs.items()
         }
 
-        # Convert to a Path and back to a string to remove any instances of `/.`
-        pattern = str(Path(pattern.replace(".", r"\.").format(**pattern_args)))
-
+        # Escape backslashes on Windows before doing any other escaping
         if sys.platform == 'win32':
-            # Escape backslashes on Windows
             pattern = pattern.replace('\\', r'\\')
 
+        # Convert to a Path and back to a string to remove any instances of `/.`
+        pattern = str(Path(pattern.replace(".", r"\.").format(**pattern_args)))
+
         for file in files:
             match = re.match(pattern, str(file.relative_to(self.root)))
             if match: