sslutil: check for OpenSSL without TLS 1.0 support in one case

It can only happen if supportedprotocols gets fixed to contain only correct
items (see the FIXME above in the file).

mercurial/sslutil.py

@@ -553,6 +553,8 b' def wrapserversocket('
     # footgun to kill security. Don't define it.
     exactprotocol = ui.config(b'devel', b'serverexactprotocol')
     if exactprotocol == b'tls1.0':
+        if b'tls1.0' not in supportedprotocols:
+            raise error.Abort(_(b'TLS 1.0 not supported by this Python'))
         protocol = ssl.PROTOCOL_TLSv1
     elif exactprotocol == b'tls1.1':
         if b'tls1.1' not in supportedprotocols: