Add hardcoded paths to macOS frameworks for Big Sur compatibility.

src/urllib3/contrib/_securetransport/bindings.py

@@ -32,7 +32,6 @@
 from __future__ import absolute_import
 
 import platform
-from ctypes.util import find_library
 from ctypes import (
     c_void_p,
     c_int32,
@@ -47,26 +46,27 @@
 from ctypes import CDLL, POINTER, CFUNCTYPE
 
 
-security_path = find_library("Security")
-if not security_path:
-    raise ImportError("The library Security could not be found")
-
-
-core_foundation_path = find_library("CoreFoundation")
-if not core_foundation_path:
-    raise ImportError("The library CoreFoundation could not be found")
-
-
 version = platform.mac_ver()[0]
 version_info = tuple(map(int, version.split(".")))
-if version_info < (10, 8):
+if platform.system() != "Darwin" or version_info < (10, 8):
     raise OSError(
         "Only OS X 10.8 and newer are supported, not %s.%s"
         % (version_info[0], version_info[1])
     )
 
-Security = CDLL(security_path, use_errno=True)
-CoreFoundation = CDLL(core_foundation_path, use_errno=True)
+security_path = "/System/Library/Frameworks/Security.framework/Security"
+core_foundation_path = (
+    "/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation"
+)
+try:
+    Security = CDLL(security_path, use_errno=True)
+except OSError:
+    raise ImportError("The library {} failed to load.".format(security_path))
+try:
+    CoreFoundation = CDLL(core_foundation_path, use_errno=True)
+except OSError:
+    raise ImportError("The library {} failed to load.".format(core_foundation_path))
+
 
 Boolean = c_bool
 CFIndex = c_long

test/contrib/test_securetransport_big_sur.py

@@ -0,0 +1,26 @@
+# -*- coding: utf-8 -*-
+import mock
+
+
+class TestSecureTransportBigSur(object):
+    """
+    Tests for macOS Big Sur's dynamic linker
+    """
+
+    @mock.patch("platform.mac_ver", return_value=("10.16", ("", "", ""), "x86_64"))
+    def test_import_current_version(self, mock_mac_ver):
+        try:
+            import urllib3.contrib.securetransport as securetransport
+
+        except ImportError:
+            securetransport = None
+        assert securetransport
+
+    @mock.patch("platform.mac_ver", return_value=("11.0", ("", "", ""), "x86_64"))
+    def test_import_future_version(self, mock_mac_ver):
+        try:
+            import urllib3.contrib.securetransport as securetransport
+
+        except ImportError:
+            securetransport = None
+        assert securetransport