Remove sys.exit from install modules and scripts

sys.exit() calls sometimes make it hard to find bugs and mask code that
does not always work properly.

https://fedorahosted.org/freeipa/ticket/5750

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaserver/install/cainstance.py

@@ -60,6 +60,7 @@ from ipapython.certdb import get_ca_nickname
 from ipapython.dn import DN
 from ipapython.ipa_log_manager import log_mgr,\
     standard_logging_setup, root_logger
+from ipapython.admintool import ScriptError
 from ipapython.secrets.kem import IPAKEMKeys
 
 from ipaserver.install import certs
@@ -590,7 +591,7 @@ class CAInstance(DogtagInstance):
         if self.external == 1:
             print("The next step is to get %s signed by your CA and re-run %s as:" % (self.csr_file, sys.argv[0]))
             print("%s --external-cert-file=/path/to/signed_certificate --external-cert-file=/path/to/external_ca_certificate" % sys.argv[0])
-            sys.exit(0)
+            raise ScriptError(rval=0)
         else:
             shutil.move(paths.CA_BACKUP_KEYS_P12,
                         paths.CACERT_P12)
@@ -1517,7 +1518,7 @@ def install_replica_ca(config, postinstall=False, ra_p12=None):
         return ca
 
     if ca.is_installed():
-        sys.exit("A CA is already configured on this system.")
+        raise ScriptError("A CA is already configured on this system.")
 
     if postinstall:
         # If installing this afterward the Apache NSS database already