DBus: Fix various pylint errors

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Status Job ID Name Coverage
  Test
passed #13454
run-appdata

00:00:07

failed #13453
run-tests

00:03:13

 
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skipped #13455
run-build
 
Name Stage Failure
failed
run-tests Test
Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
************* Module gajim.common.modules.jingle
gajim/common/modules/jingle.py:248:45: E0602: Undefined variable 'session' (undefined-variable)

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ERROR: Job failed: exit status 1