Ensure all tox commands use envpython

tox.ini

@@ -15,11 +15,11 @@ deps =
     py26: unittest2
 
 commands =
-    python -m unittest discover -s {toxinidir}/tests {posargs}
+    {envpython} -m unittest discover -s {toxinidir}/tests {posargs}
 
 [testenv:py26]
 commands =
-    python -m unittest2.__main__ discover -s {toxinidir}/tests {posargs}
+    {envpython} -m unittest2.__main__ discover -s {toxinidir}/tests {posargs}
 
 [testenv:el7]
 basepython = python2.7
@@ -47,7 +47,7 @@ deps =
     flake8
 
 commands =
-    flake8 *.py tests/*.py examples/*.py
+    {envpython} -m flake8 *.py tests/*.py examples/*.py
 
 [testenv:pylint]
 skip_install = True
@@ -59,7 +59,7 @@ deps =
     pyenchant
 
 commands =
-    pylint enlighten setup setup_helpers tests examples
+    {envpython} -m pylint enlighten setup setup_helpers tests examples
 
 [testenv:lint]
 skip_install = True
@@ -80,8 +80,8 @@ deps =
     coverage
 
 commands =
-    coverage run -m unittest discover -s {toxinidir}/tests {posargs}
-    coverage report
+    {envpython} -m coverage run -m unittest discover -s {toxinidir}/tests {posargs}
+    {envpython} -m coverage report
 
 [testenv:codecov]
 basepython = python3.6
@@ -92,7 +92,7 @@ deps =
 
 commands =
     {[testenv:coverage]commands}
-    codecov
+    {envpython} -m codecov
 
 [testenv:docs]
 basepython = python3.6
@@ -102,7 +102,7 @@ deps =
     sphinx_rtd_theme
 
 commands=
-    python setup.py spelling
-    python setup_helpers.py spelling
-    python setup.py html
+    {envpython} setup.py spelling
+    {envpython} setup_helpers.py spelling
+    {envpython} setup.py html