Pass exception to log.exception as it is not called from within an except: clause. Add Python 3.8 test support, drop Python 3.4 test support.

.travis.yml

@@ -2,9 +2,9 @@ language: python
 
 python:
   - 2.7
-  - 3.4
   - 3.5
   - 3.6
+  - 3.8
   
 install: pip install tox-travis codecov
 

dsmr_parser/clients/protocol.py

@@ -95,7 +95,7 @@ class DSMRProtocol(asyncio.Protocol):
     def connection_lost(self, exc):
         """Stop when connection is lost."""
         if exc:
-            self.log.exception('disconnected due to exception')
+            self.log.exception('disconnected due to exception', exc_info=exc)
         else:
             self.log.info('disconnected because of close/abort.')
         self._closed.set()

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py34,py35,py36,py37
+envlist = py35,py36,py37,py38
 
 [testenv]
 deps=