client: use exceptions instead of return states

Python has builtin exceptions which can be used very well to handling
errors in python instead of returning error states (C style)

Exception will allow better client-server integration in future

https://fedorahosted.org/freeipa/ticket/6392

Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>

client/ipa-client-install

@@ -30,6 +30,7 @@ from ipaclient.install import client
 from ipapython.ipa_log_manager import standard_logging_setup, root_logger
 from ipaplatform.paths import paths
 from ipapython import version
+from ipapython.admintool import ScriptError
 from ipapython.config import IPAOptionParser
 from ipalib import x509
 from ipalib.util import normalize_hostname, validate_domain_name
@@ -230,21 +231,19 @@ def main():
     root_logger.debug('IPA version %s' % version.VENDOR_VERSION)
 
     if options.uninstall:
-        rval_check = client.uninstall_check(options)
-        if rval_check != client.SUCCESS:
-            return rval_check
-
-        return client.uninstall(options)
+        client.uninstall_check(options)
+        client.uninstall(options)
     else:
-        rval_check = client.install_check(options)
-        if rval_check != client.SUCCESS:
-            return rval_check
-
-        return client.install(options)
+        client.install_check(options)
+        client.install(options)
 
 if __name__ == "__main__":
     try:
         sys.exit(main())
+    except ScriptError as e:
+        if e.rval != client.SUCCESS and e.msg:
+            root_logger.error(e.msg)
+        sys.exit(e.rval)
     except KeyboardInterrupt:
         sys.exit(1)
     except RuntimeError as e: