Ignore header difference for osx_framework_user

src/pip/_internal/locations/__init__.py

@@ -11,6 +11,7 @@
     USER_CACHE_DIR,
     get_major_minor_version,
     get_src_prefix,
+    is_osx_framework,
     site_packages,
     user_site,
 )
@@ -115,6 +116,19 @@ def get_scheme(
         if skip_pypy_special_case:
             continue
 
+        # sysconfig's ``osx_framework_user`` does not include ``pythonX.Y`` in
+        # the ``include`` value, but distutils's ``headers`` does. We'll let
+        # CPython decide whether this is a bug or feature. See bpo-43948.
+        skip_osx_framework_user_special_case = (
+            user
+            and is_osx_framework()
+            and k == "headers"
+            and old_v.parent == new_v
+            and old_v.name.startswith("python")
+        )
+        if skip_osx_framework_user_special_case:
+            continue
+
         warned.append(_warn_if_mismatch(old_v, new_v, key=f"scheme.{k}"))
 
     if any(warned):

src/pip/_internal/locations/_sysconfig.py

@@ -9,7 +9,7 @@
 from pip._internal.models.scheme import SCHEME_KEYS, Scheme
 from pip._internal.utils.virtualenv import running_under_virtualenv
 
-from .base import get_major_minor_version
+from .base import get_major_minor_version, is_osx_framework
 
 logger = logging.getLogger(__name__)
 
@@ -25,10 +25,6 @@
 _AVAILABLE_SCHEMES = set(sysconfig.get_scheme_names())
 
 
-def _is_osx_framework() -> bool:
-    return sysconfig.get_config_var("PYTHONFRAMEWORK")
-
-
 def _infer_prefix() -> str:
     """Try to find a prefix scheme for the current platform.
 
@@ -43,7 +39,7 @@ def _infer_prefix() -> str:
 
     If none of the above works, fall back to ``posix_prefix``.
     """
-    os_framework_global = _is_osx_framework() and not running_under_virtualenv()
+    os_framework_global = is_osx_framework() and not running_under_virtualenv()
     if os_framework_global and "osx_framework_library" in _AVAILABLE_SCHEMES:
         return "osx_framework_library"
     implementation_suffixed = f"{sys.implementation.name}_{os.name}"
@@ -61,7 +57,7 @@ def _infer_prefix() -> str:
 
 def _infer_user() -> str:
     """Try to find a user scheme for the current platform."""
-    if _is_osx_framework() and not running_under_virtualenv():
+    if is_osx_framework() and not running_under_virtualenv():
         suffixed = "osx_framework_user"
     else:
         suffixed = f"{os.name}_user"

src/pip/_internal/locations/base.py

@@ -44,3 +44,7 @@ def get_src_prefix() -> str:
     user_site: typing.Optional[str] = site.getusersitepackages()
 except AttributeError:
     user_site = site.USER_SITE
+
+
+def is_osx_framework() -> bool:
+    return bool(sysconfig.get_config_var("PYTHONFRAMEWORK"))