Use re.escape for windows paths

src/pip/_internal/req/req_file.py

@@ -367,12 +367,12 @@ def _parse_and_recurse(
                 if req_path in self._parsed_files.keys():
                     initial_file = self._parsed_files[req_path]
                     tail = (
-                        f"and again in {initial_file}"
+                        f" and again in {initial_file}"
                         if initial_file is not None
                         else ""
                     )
                     raise RequirementsFileParseError(
-                        f"{req_path} recursively references itself in {filename} {tail}"
+                        f"{req_path} recursively references itself in {filename}{tail}"
                     )
                 # Keeping a track where was each file first included in
                 self._parsed_files[req_path] = filename

tests/unit/test_req_file.py

@@ -1,6 +1,7 @@
 import collections
 import logging
 import os
+import re
 import textwrap
 from optparse import Values
 from pathlib import Path
@@ -78,12 +79,6 @@ def parse_reqfile(
         )
 
 
-def path_to_string(p: Path) -> str:
-    # Escape the back slashes in windows path before using it
-    # in a regex
-    return str(p).replace("\\", "\\\\")
-
-
 def test_read_file_url(tmp_path: Path, session: PipSession) -> None:
     reqs = tmp_path.joinpath("requirements.txt")
     reqs.write_text("foo")
@@ -365,8 +360,8 @@ def test_recursive_requirements_file(
         with pytest.raises(
             RequirementsFileParseError,
             match=(
-                f"{path_to_string(req_files[0])} recursively references itself"
-                f" in {path_to_string(req_files[req_file_count - 1])}"
+                f"{re.escape(str(req_files[0]))} recursively references itself"
+                f" in {re.escape(str(req_files[req_file_count - 1]))}"
             ),
         ):
             list(parse_requirements(filename=str(req_files[0]), session=session))
@@ -379,10 +374,10 @@ def test_recursive_requirements_file(
         with pytest.raises(
             RequirementsFileParseError,
             match=(
-                f"{path_to_string(req_files[req_file_count - 2])} recursively"
+                f"{re.escape(str(req_files[req_file_count - 2]))} recursively"
                 " references itself in"
-                f" {path_to_string(req_files[req_file_count - 1])} and again in"
-                f" {path_to_string(req_files[req_file_count - 3])}"
+                f" {re.escape(str(req_files[req_file_count - 1]))} and again in"
+                f" {re.escape(str(req_files[req_file_count - 3]))}"
             ),
         ):
             list(parse_requirements(filename=str(req_files[0]), session=session))
@@ -402,8 +397,8 @@ def test_recursive_relative_requirements_file(
         with pytest.raises(
             RequirementsFileParseError,
             match=(
-                f"{path_to_string(root_req_file)} recursively references itself in"
-                f" {path_to_string(level_2_req_file)}"
+                f"{re.escape(str(root_req_file))} recursively references itself in"
+                f" {re.escape(str(level_2_req_file))}"
             ),
         ):
             list(parse_requirements(filename=str(root_req_file), session=session))