Issue 50952 - SSCA lacks basicConstraint:CA

Bug Description:
`capture_output` was introduced in python 3.7 and
on earlier versions this code produces TypeError.

Fix Description:
Make it compatible with python 3.6 by setting `stderr`
and `stdout` to PIPE.

Fixes: https://pagure.io/389-ds-base/issue/50952

Reviewed by: mhonek (Thanks!)

src/lib389/lib389/nss_ssl.py

@@ -19,7 +19,7 @@
 # from nss import nss
 import subprocess
 from datetime import datetime, timedelta, date
-from subprocess import check_output, run
+from subprocess import check_output, run, PIPE
 from lib389.passwd import password_generate
 from lib389.lint import DSCERTLE0001, DSCERTLE0002
 from lib389.utils import ensure_str, format_cmd_list
@@ -254,7 +254,7 @@ def create_rsa_ca(self, months=VALID):
         ]
         cmd_input = b'y\n\n'  # responses to certutil questions
         self.log.debug("nss cmd: %s", format_cmd_list(cmd))
-        result = ensure_str(run(cmd, check=True, capture_output=True, input=cmd_input).stdout)
+        result = ensure_str(run(cmd, check=True, stderr=PIPE, stdout=PIPE, input=cmd_input).stdout)
         self.log.debug("nss output: %s", result)
         # Now extract the CAcert to a well know place.
         # This allows us to point the cacert dir here and it "just works"