Various python3 related changes

- Use relative import for grgsm's modules
- Convert map to list
- Remove the hier_block.py workaround as as gnuradio 3.7 is no longer
  supported in this branch

Change-Id: I5ca8fd340823996e8c444aaf18ddacd85c92ab1c
diff --git a/python/demapping/gsm_bcch_ccch_demapper.py b/python/demapping/gsm_bcch_ccch_demapper.py
index e036831..06baa62 100644
--- a/python/demapping/gsm_bcch_ccch_demapper.py
+++ b/python/demapping/gsm_bcch_ccch_demapper.py
@@ -32,10 +32,10 @@
 import grgsm
 
 
-class gsm_bcch_ccch_demapper(grgsm.hier_block):
+class gsm_bcch_ccch_demapper(gr.hier_block2):
 
     def __init__(self, timeslot_nr=0):
-        grgsm.hier_block.__init__(
+        gr.hier_block2.__init__(
             self, "BCCH + CCCH demapper",
             gr.io_signature(0, 0, 0),
             gr.io_signature(0, 0, 0),