First round of clean-ups of imports and unused variables

Run pyflakes src/osmo_gsm_tester and then address the first
round of problems.

Change-Id: I02f1d89078dfdf37d53e2e20811bf36fb14ec3b0
diff --git a/src/osmo_gsm_tester/bts_osmotrx.py b/src/osmo_gsm_tester/bts_osmotrx.py
index 92b726c..86afeec 100644
--- a/src/osmo_gsm_tester/bts_osmotrx.py
+++ b/src/osmo_gsm_tester/bts_osmotrx.py
@@ -20,9 +20,8 @@
 import os
 import stat
 import pprint
-import tempfile
 from abc import ABCMeta, abstractmethod
-from . import log, config, util, template, process, pcu_osmo, bts_osmo
+from . import log, config, util, template, process, bts_osmo
 from .event_loop import MainLoop
 
 class OsmoBtsTrx(bts_osmo.OsmoBtsMainUnit):