switched to python3.6 explicitly for basepython

tox.ini

@@ -24,7 +24,7 @@ deps =
 commands = nosetests []
 
 [testenv:doctest]
-basepython = python3
+basepython = python3.6
 deps =
     nose
 setenv =
@@ -63,26 +63,26 @@ commands = {[testenv:fuzz]commands}
 
 
 [testenv:pylint]
-basepython = python3
+basepython = python3.6
 skip_install = true
 deps = pylint
 commands = {toxinidir}/helpers/call_and_write_log.py \
                "pylint --rcfile=setup.cfg abydos" 0
 
 [testenv:pydocstyle]
-basepython = python3
+basepython = python3.6
 skip_install = true
 deps = pydocstyle
 commands = {toxinidir}/helpers/call_and_write_log.py "pydocstyle --count ." 0
 
 [testenv:pycodestyle]
-basepython = python3
+basepython = python3.6
 skip_install = true
 deps = pycodestyle
 commands = {toxinidir}/helpers/call_and_write_log.py "pycodestyle ." 0
 
 [testenv:flake8]
-basepython = python3
+basepython = python3.6
 skip_install = true
 deps =
     flake8
@@ -113,14 +113,14 @@ commands = {toxinidir}/helpers/call_and_write_log.py \
                "flake8 {toxinidir} --htmldir={toxinidir}/flake8" 0
 
 [testenv:doc8]
-basepython = python3
+basepython = python3.6
 skip_install = true
 deps = doc8
 commands = {toxinidir}/helpers/call_and_write_log.py "doc8 {toxinidir}" 0
 
 [testenv:docs]
 changedir = docs
-basepython = python3
+basepython = python3.6
 whitelist_externals=make
 deps =
     sphinx
@@ -138,20 +138,20 @@ commands =
     sphinx-build -b coverage -d {envtmpdir}/doctrees . _build/coverage
 
 [testenv:badges]
-basepython = python3
+basepython = python3.6
 skip_install = true
 commands = python {toxinidir}/badge_update.py
 
 [testenv:black]
 changedir = {toxinidir}
-basepython = python3
+basepython = python3.6
 skip_install = true
 deps = black
 commands = black .
 
 [testenv:dist]
 changedir = {toxinidir}
-basepython = python3
+basepython = python3.6
 skip_install = true
 commands =
     python setup.py sdist