Replace SSLCertVerificationError with CertificateError for py36

This exception was added in python 3.7. Use CertificateError
instead which is an alias and will work with older python releases.

https://bugzilla.redhat.com/show_bug.cgi?id=1858318

Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>

ipaserver/install/server/upgrade.py

@@ -686,7 +686,7 @@ def http_certificate_ensure_ipa_ca_dnsname(http):
 
     try:
         cert.match_hostname(expect)
-    except ssl.SSLCertVerificationError:
+    except ssl.CertificateError:
         if certs.is_ipa_issued_cert(api, cert):
             request_id = certmonger.get_request_id(
                 {'cert-file': paths.HTTPD_CERT_FILE})