Fix import error messages and a tab

plugins/tor/tor_

@@ -58,10 +58,15 @@ import json
 import os
 import sys
 
-import GeoIP
-import stem
-import stem.control
-import stem.connection
+try:
+    import GeoIP
+    import stem
+    import stem.control
+    import stem.connection
+except ImportError:
+    # missing dependencies are reported via "autoconf"
+    # thus failure is acceptable here
+    pass
 
 default_torcachefile = 'munin_tor_country_stats.json'
 default_torconnectmethod = 'port'
@@ -141,7 +146,7 @@ class TorPlugin(object):
             import stem
 
         except ImportError as e:
-            print('no ({})'.format(e))
+            print('no (failed to import the required python module "stem": {})'.format(e))
 
         try:
             import GeoIP 
@@ -528,7 +533,7 @@ def main():
             provider.fetch()
         else:
             print('Unknown parameter "{}"'.format(param), file=sys.stderr)
-	    sys.exit(1)
+            sys.exit(1)
 
 if __name__ == '__main__':
     main()