An initial attempt to skip collection on macOS API module. Doesn't wo…

…rk because mac_ver doesn't work on newer macs with older Pythons. Ref #529.

conftest.py

@@ -1,8 +1,29 @@
+import sys
 import platform
 
 collect_ignore = ["hook-keyring.backend.py"]
 
-if platform.system() != 'Darwin':
-    collect_ignore.append('keyring/backends/macOS/api.py')
+
+def macos_api_ignore():
+    """
+    Starting with macOS 11, the security API becomes
+    non-viable except on universal2 binaries.
+
+    Ref #525.
+    """
+
+    def make_ver(string):
+        return tuple(map(int, string.split('.')))
+
+    release, _, _ = platform.mac_ver()
+
+    return (
+        platform.system() != 'Darwin'
+        or make_ver(release) > (11,)
+        and sys.version_info < (3, 8, 7)
+    )
+
+
+collect_ignore.extend(['keyring/backends/macOS/api.py'] * macos_api_ignore())
 
 collect_ignore.append('keyring/devpi_client.py')