VOL-2241:  Python 3 migration

 - rename adapter class file and remove unneeded __init__ to make imports work without major rearrange
 - venv and Dockerfile fixups needed for new pyvoltha (cannot install old first)
 - clean up yaml config file as it contained empty entries that failed to parse
 - clean up imports
 - remove itervalues iter*
 - convert to list() as needed
 - test with python 3.6
 - skip non-dict items in tcont loop
 - update to voltha-protos 2.1.0
 - migrate socketserver and simplehttpserver to python3 import

Change-Id: Id8efa72b6796a3055b1927716503a33544bb6548
diff --git a/python/adapters/brcm_openomci_onu/onu_tcont.py b/python/adapters/brcm_openomci_onu/onu_tcont.py
index aabaed8..80e98a0 100644
--- a/python/adapters/brcm_openomci_onu/onu_tcont.py
+++ b/python/adapters/brcm_openomci_onu/onu_tcont.py
@@ -13,10 +13,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import absolute_import
 import structlog
-from twisted.internet.defer import  inlineCallbacks, returnValue, succeed
-from pyvoltha.adapters.extensions.omci.omci_me import *
-from pyvoltha.adapters.extensions.omci.omci_defs import *
+from twisted.internet.defer import inlineCallbacks, returnValue
+from pyvoltha.adapters.extensions.omci.omci_me import TcontFrame
+from pyvoltha.adapters.extensions.omci.omci_defs import ReasonCodes
 
 RC = ReasonCodes