raise FileNotFoundError for missing TLS material

Would you accept a PR which changes the existing OSError for missing TLS material to FileNotFoundError?

e.g.:

            if conn.cert_file and not os.path.exists(conn.cert_file):
                raise OSError(
                    f"Could not find the TLS certificate file, "
                    f"invalid path: {conn.cert_file}"
                )

becomes something like:

            if conn.cert_file and not os.path.exists(conn.cert_file):
                from errno import ENOENT
                raise FileNotFoundError(
                    ENOENT,
                    "Could not find the TLS certificate file, invalid path",
                    str(conn.cert_file)
                )

Our use case is that there are temporary conditions where the files don't exist and it'd be nicer to handle FileNotFoundError specifically and be able to compare the .filename attribute rather than the more general OSError and test str(excp).endswith(...). As FileNotFoundError is a subclass of OSError existing try/excepts continue to work but it would change the string representation:

>>> str(OSError("Could not find the TLS certificate file, invalid path: filename"))
'Could not find the TLS certificate file, invalid path: filename'
>>> str(FileNotFoundError(errno.ENOENT, "Could not find the TLS certificate file, invalid path", "filename"))
"[Errno 2] Could not find the TLS certificate file, invalid path: 'filename'"

Search the repository for the conn.cert_file existence check shown in the issue and inspect its nearby tests or callers. Confirm the current OSError behavior and identify coverage for missing TLS material. Done means missing certificate paths raise FileNotFoundError with ENOENT and the filename available for targeted handling, while existing OSError handlers continue to work.