use multiline regex (#402)

* use multiline regex'

* re.escape

* doctest pattern too

Author: MarcoGorelli

nbqa/__main__.py

@@ -141,18 +141,18 @@ def _map_python_line_to_nb_lines(
         Stdout with references to temporary Python file's lines replaced with references
         to notebook's cells and lines.
     """
-    pattern = rf"(?<={notebook.name}:)\d+"
+    pattern = rf"(?<=^{re.escape(str(notebook))}:)\d+"
 
     def substitution(match: Match[str]) -> str:
         """Replace Python line with corresponding Jupyter notebook cell."""
         return str(cell_mapping[int(match.group())])
 
-    out = re.sub(pattern, substitution, out)
+    out = re.sub(pattern, substitution, out, flags=re.MULTILINE)
 
     # doctest pattern
-    pattern = rf'(?<={notebook.name}", line )\d+'
-    if re.search(pattern, out) is not None:
-        out = re.sub(pattern, substitution, out)
+    pattern = rf'(?<=^File "{re.escape(str(notebook))}", line )\d+'
+    if re.search(pattern, out, flags=re.MULTILINE) is not None:
+        out = re.sub(pattern, substitution, out, flags=re.MULTILINE)
         out = out.replace(f'{notebook.name}", line ', f'{notebook.name}", ')
 
     return out