Set stderr loghandler in isbg_run

Setting the log handler that logs everything to stderr only in the
`isbg_run` method meant for when isbg is run as command / top level
script.

When isbg is run as a library, the caller is responsible for setting up
log output. If we add a log handler this can lead to messages being
duplicated.

isbg/isbg.py

@@ -701,12 +701,6 @@ def spamlearn(self):
         return result
 
     def do_isbg(self):
-        ch = logging.StreamHandler()
-        self.logger.addHandler(ch)
-        if self.verbose:
-            ch.setLevel(logging.DEBUG)
-        else:
-            ch.setLevel(logging.INFO)
 
         if self.spamc:
             self.satest = ["spamc", "-c"]
@@ -850,6 +844,12 @@ def do_isbg(self):
 def isbg_run():
     isbg = ISBG()
     isbg.parse_args()
+    ch = logging.StreamHandler()
+    isbg.logger.addHandler(ch)
+    if self.verbose:
+        ch.setLevel(logging.DEBUG)
+    else:
+        ch.setLevel(logging.INFO)
     isbg.do_isbg()
 
 if __name__ == '__main__':