Add python 3 section to tox

tox.ini

@@ -31,7 +31,6 @@ deps =
     mock
     slimit
     pillow
-    py2-ipaddress
 whitelist_externals = py.test
 commands = {envpython} setup.py test
 
@@ -49,7 +48,7 @@ commands = py.test --basetemp=_pytest_temp deluge
 
 [testenv:pydef]
 commands =
-    python -c "import libtorrent as lt; print lt.__version__"
+    python -c "import libtorrent as lt; print(lt.__version__)"
     py.test -v --basetemp=_pytest_temp -s -m "not (todo or gtkui)" deluge/tests
 
 [testenv:pygtkui]
@@ -78,9 +77,15 @@ commands =
     py.test -v --basetemp=_pytest_temp -s deluge/plugins
 
 [testenv:py27]
+deps =
+    {[testenv]deps}
+    py2-ipaddress
 basepython = python2.7
 commands = {[testenv:pydef]commands}
 
+[testenv:py3]
+basepython = python3
+commands = {[testenv:pydef]commands}
 
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 # Code style verification