Update macOS SSL certificates (#447)

Update macOS SSL certificates using latest `certifi` certificate bundle.

Co-authored-by: Yannick Jadoul <yannick.jadoul@belgacom.net>
Co-authored-by: Matthieu Darbois <mayeut@users.noreply.github.com>

cibuildwheel/resources/install_certifi.py

@@ -0,0 +1,52 @@
+# Based on: https://github.com/python/cpython/blob/master/Mac/BuildScript/resources/install_certificates.command
+
+# install_certifi.py
+#
+# sample script to install or update a set of default Root Certificates
+# for the ssl module.  Uses the certificates provided by the certifi package:
+#       https://pypi.org/project/certifi/
+
+import os
+import os.path
+import ssl
+import stat
+import subprocess
+import sys
+
+STAT_0o775 = (stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR
+              | stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP
+              | stat.S_IROTH | stat.S_IXOTH)
+
+if sys.version_info[0] == 2:
+    FileNotFoundError = OSError
+
+
+def main():
+    openssl_dir, openssl_cafile = os.path.split(
+        ssl.get_default_verify_paths().openssl_cafile)
+    print(" -- pip install --upgrade certifi")
+    subprocess.check_call([sys.executable,
+                           "-E", "-s", "-m", "pip", "install", "--upgrade", "certifi"])
+
+    import certifi
+    # change working directory to the default SSL directory
+    if sys.version_info[0:2] == (3, 5):
+        os.makedirs(openssl_dir, exist_ok=True, mode=0o775)
+    os.chdir(openssl_dir)
+    relpath_to_certifi_cafile = os.path.relpath(certifi.where())
+
+    print(" -- removing any existing file or link")
+    try:
+        os.remove(openssl_cafile)
+    except FileNotFoundError:
+        pass
+    print(" -- creating symlink to certifi certificate bundle")
+    os.symlink(relpath_to_certifi_cafile, openssl_cafile)
+
+    print(" -- setting permissions")
+    os.chmod(openssl_cafile, STAT_0o775)
+    print(" -- update complete")
+
+
+if __name__ == '__main__':
+    main()