Fix some errors with pylint

wo/cli/plugins/site_functions.py

@@ -17,7 +17,8 @@ from wo.core.aptget import WOAptGet
 from wo.core.fileutils import WOFileUtils
 from wo.core.git import WOGit
 from wo.core.logging import Log
-from wo.core.mysql import WOMysql
+from wo.core.mysql import (MySQLConnectionError, StatementExcecutionError,
+                           WOMysql)
 from wo.core.services import WOService
 from wo.core.shellexec import CommandExecutionError, WOShellExec
 from wo.core.sslutils import SSL
@@ -1622,4 +1623,4 @@ def setupngxblocker(self, domain, block=True):
                 self, '/var/www/{0}/conf/nginx/ngxblocker.disabled'
                 .format(domain), '/var/www/{0}/conf/nginx/ngxblocker'
                 .format(domain))
-        return 0
+        return 0