Fuzzer testing: less strict special-case regex match passthrough for multi-line EOF exceptions (#1998)

fuzz.py

@@ -50,9 +50,9 @@ def test_idempotent_any_syntatically_valid_python(
         # TODO: remove this try-except block when issues are resolved.
         return
     except TokenError as e:
-        if (
+        if (  # Special-case logic for backslashes followed by newlines or end-of-input
             e.args[0] == "EOF in multi-line statement"
-            and re.search(r"\r?\n\\\r?\n", src_contents) is not None
+            and re.search(r"\\($|\r?\n)", src_contents) is not None
         ):
             # This is a bug - if it's valid Python code, as above, Black should be
             # able to cope with it.  See issue #1012.