Fix retry handlers

 * readlines() - invalid method for Exception,
  which brakes retry logic in code

Change-Id: I96ac4344cff6d5a0a1a351f983bed31f071bce0a
Prod-related: PROD-28636 (PROD:28636)
(cherry picked from commit 06b7493100f7a69a20de4f68fc60fffd2f28fedd)
diff --git a/_modules/maasng.py b/_modules/maasng.py
index 29a2c07..879babe 100644
--- a/_modules/maasng.py
+++ b/_modules/maasng.py
@@ -1320,10 +1320,7 @@
             result["changes"] = "Fabric  {0} updated".format(json_res["name"])
     except Exception as inst:
         LOG.debug("create_fabric data:{}".format(data))
-        try:
-            m = inst.readlines()
-        except:
-            m = inst.message
+        m = inst.message
         LOG.error("Message:{0}".format(m))
         result['result'] = False
         result['comment'] = 'Error creating fabric: {0}'.format(name)
@@ -1370,7 +1367,7 @@
         json_res = json.loads(
             maas.get(u'api/2.0/fabrics/{0}/vlans/'.format(fabric_id)).read())
     except Exception as inst:
-        m = inst.readlines()
+        m = inst.message
         LOG.error("Message:{0}".format(m))
     LOG.debug(json_res)
     for item in json_res:
@@ -1449,10 +1446,7 @@
                 u'api/2.0/fabrics/{0}/vlans/'.format(fabric_id), None, **data).read())
     except Exception as inst:
         LOG.debug("create_vlan_in_fabric data:{}".format(data))
-        try:
-            m = inst.readlines()
-        except:
-            m = inst.message
+        m = inst.message
         LOG.error("Message:{0}".format(m))
         result['result'] = False
         result['comment'] = 'Error updating vlan: {0}'.format(name)
@@ -1516,10 +1510,7 @@
                 maas.post(u"api/2.0/subnets/", None, **data).read())
     except Exception as inst:
         LOG.debug("create_subnet data:{}".format(data))
-        try:
-            m = inst.readlines()
-        except:
-            m = inst.message
+        m = inst.message
         LOG.error("Message:{0}".format(m))
         result['result'] = False
         result['comment'] = 'Error creating subnet: {0}'.format(name)
@@ -1611,10 +1602,7 @@
         json_res = json.loads(
             maas.post(u"api/2.0/ipranges/", None, **data).read())
     except Exception as inst:
-        try:
-            m = inst.readlines()
-        except:
-            m = inst.message
+        m = inst.message
         LOG.error("Message:{0}".format(m))
         result['result'] = False
         result['comment'] = 'Error creating iprange:{0}'.format(_name)
@@ -1960,7 +1948,7 @@
                 maas.post(u'api/2.0/boot-sources/{0}/selections/'.format(bs_id), None,
                           **data).read())
         except Exception as inst:
-            m = inst.readlines()
+            m = inst.message
             LOG.warning("boot_source_selections "
                         "catch error during processing. Most-probably, "
                         "streams data not imported yet.\nSleep:{}s "