gh-94637: Release GIL in SSLContext.set_default_verify_paths (GH-94658)

(cherry picked from commit 78307c7)

Co-authored-by: Christian Heimes <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/Library/2022-07-07-15-46-55.gh-issue-94637.IYEiUM.rst

@@ -0,0 +1,3 @@
+:meth:`SSLContext.set_default_verify_paths` now releases the GIL around
+``SSL_CTX_set_default_verify_paths`` call. The function call performs I/O
+and CPU intensive work.

Modules/_ssl.c

@@ -4305,7 +4305,11 @@ static PyObject *
 _ssl__SSLContext_set_default_verify_paths_impl(PySSLContext *self)
 /*[clinic end generated code: output=0bee74e6e09deaaa input=35f3408021463d74]*/
 {
-    if (!SSL_CTX_set_default_verify_paths(self->ctx)) {
+    int rc;
+    Py_BEGIN_ALLOW_THREADS
+    rc = SSL_CTX_set_default_verify_paths(self->ctx);
+    Py_END_ALLOW_THREADS
+    if (!rc) {
         _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
         return NULL;
     }