Fix invalid escape sequence SyntaxWarnings

The two ASCII-art literals and the parse_multi_value_header() regex used
unrecognized escape sequences (\_, \ , \s), which emit a SyntaxWarning on
Python 3.12+ (DeprecationWarning earlier) and will become a SyntaxError in a
future Python. Make them raw strings; the rendered art and regex behaviour are
byte-for-byte unchanged (verified against the prior values).

Adds a regression test that compiles every module in the httpbin package with
escape-sequence warnings escalated to errors.

Closes #62. Supersedes #55.

Co-Authored-By: gesh <gesh@gesh.uni.cx>

Author: kevin1024

httpbin/helpers.py

@@ -29,7 +29,7 @@
 from .structures import CaseInsensitiveDict
 
 
-ASCII_ART = """
+ASCII_ART = r'''
     -=[ teapot ]=-
 
        _...._
@@ -38,8 +38,8 @@
     \_;`"---"`|//
       |       ;/
       \_     _/
-        `\"\"\"`
-"""
+        `"""`
+'''
 
 REDIRECT_LOCATION = '/redirect/1'
 
@@ -74,10 +74,10 @@
     'image/*'
 ]
 
-ANGRY_ASCII ="""
+ANGRY_ASCII = r"""
           .-''''''-.
         .' _      _ '.
-       /   O      O   \\
+       /   O      O   \
       :                :
       |                |
       :       __       :
@@ -441,7 +441,7 @@ def parse_multi_value_header(header_str):
     if header_str:
         parts = header_str.split(',')
         for part in parts:
-            match = re.search('\s*(W/)?\"?([^"]*)\"?\s*', part)
+            match = re.search(r'\s*(W/)?\"?([^"]*)\"?\s*', part)
             if match is not None:
                 parsed_parts.append(match.group(2))
     return parsed_parts

tests/test_httpbin.py

@@ -823,6 +823,27 @@ def test_index_falls_back_to_static_page_without_flasgger(self):
         self.assertEqual(result.returncode, 0, result.stderr)
         self.assertIn("OK", result.stdout)
 
+    def test_sources_have_no_invalid_escape_sequences(self):
+        """Every module in the httpbin package compiles without escape-sequence
+        warnings. Invalid escapes are a SyntaxWarning on 3.12+ (DeprecationWarning
+        earlier) and will become a SyntaxError in a future Python."""
+        import glob
+        import warnings
+
+        pkg_dir = os.path.dirname(httpbin.__file__)
+        py_files = glob.glob(os.path.join(pkg_dir, "**", "*.py"), recursive=True)
+        self.assertTrue(py_files, "no source files found")
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", SyntaxWarning)
+            warnings.simplefilter("error", DeprecationWarning)
+            for path in py_files:
+                with open(path, encoding="utf-8") as f:
+                    src = f.read()
+                try:
+                    compile(src, path, "exec")
+                except (SyntaxWarning, DeprecationWarning) as exc:
+                    self.fail("{}: {}".format(path, exc))
+
     def test_parse_multi_value_header(self):
         self.assertEqual(parse_multi_value_header('xyzzy'), [ "xyzzy" ])
         self.assertEqual(parse_multi_value_header('"xyzzy"'), [ "xyzzy" ])