Modification in tox.ini

* move flake8 to a more generic lint / linter section and make that useable with Python 2 & 3
* introduce constraints.txt which for the start is empty, but could be used to pin / or exclude bad versions.

constraints.txt

@@ -0,0 +1,3 @@
+# Constraints for Python Packages
+# -----------------------------------------------
+# Pin Versions / Version Ranges if necessary.

tox.ini

@@ -6,9 +6,10 @@ envlist =
     py35,
     py36,
     py36-datetime,
+    pypy,
     docs,
-    isort,
-    flake8,
+    lint-py2,
+    lint-py3,
     coverage,
 
 skip_missing_interpreters = False
@@ -20,71 +21,124 @@ extras =
     test
 
 commands =
-    pytest --cov=src --cov-report=xml --html=reports/pytest/report-{envname}.html --doctest-glob=*.rst --self-contained-html {posargs}
+    pytest --cov=src --cov-report=xml --html=reports/pytest/report-{envname}.html --self-contained-html {posargs}
     pytest --doctest-modules src/RestrictedPython/compile.py {posargs}
 
 setenv =
   COVERAGE_FILE=.coverage.{envname}
 
 deps =
+    -cconstraints.txt
     pytest-cov
     pytest-remove-stale-bytecode
     pytest-html
 
 [testenv:py27-datetime]
 basepython = python2.7
 deps =
+    -cconstraints.txt
     {[testenv]deps}
     DateTime
 
 [testenv:py36-datetime]
 basepython = python3.6
 deps =
+    -cconstraints.txt
     {[testenv]deps}
     DateTime
 
+<<<<<<< HEAD
+=======
+[testenv:py27-rp3]
+basepython = python2.7
+commands =
+    coverage run {envbindir}/zope-testrunner --path=src/RestrictedPython --all {posargs}
+deps =
+    -cconstraints.txt
+    .[test]
+    zope.testrunner
+    coverage
+
+>>>>>>> Modification in tox.ini
 [testenv:coverage]
 basepython = python2.7
-deps = coverage
+skip_install = true
+
+deps =
+    -cconstraints.txt
+    coverage
+
 setenv =
   COVERAGE_FILE=.coverage
 
-skip_install = true
 commands =
     coverage erase
     coverage combine
     coverage html
     coverage xml
     coverage report
 
-[testenv:isort]
-basepython = python2.7
-deps = isort
-commands =
-    isort --check-only --recursive {toxinidir}/src {toxinidir}/tests {posargs}
-
 [testenv:isort-apply]
 basepython = python2.7
-deps = isort
+skip_install = true
+deps =
+    -cconstraints.txt
+    isort
+
 commands =
     isort --apply --recursive {toxinidir}/src {toxinidir}/tests {posargs}
 
-[testenv:flake8]
-basepython = python2.7
+[lint]
+skip_install = true
+
 deps =
+    -cconstraints.txt
     flake8
+    # helper to generate HTML reports:
     flake8-html
-    flake8-debugger
-    flake8-todo
+    # Useful flake8 plugins that are Python and Plone specific:
+    isort
 
 commands =
-    - flake8 --format=html --htmldir={toxinidir}/reports/flake8 --doctests src tests setup.py {posargs}
-    flake8 --doctests src tests setup.py {posargs}
+    mkdir -p {toxinidir}/reports/flake8
+    isort --check-only --recursive {toxinidir}/src {toxinidir}/tests setup.py
+    - flake8 --format=html --htmldir={toxinidir}/reports/flake8 --doctests src tests setup.py
+    flake8 src tests setup.py --doctests
+
+whitelist_externals =
+    mkdir
+
+[testenv:lint-py2]
+basepython = python2
+skip_install = true
+deps = {[lint]deps}
+commands = {[lint]commands}
+whitelist_externals = {[lint]whitelist_externals}
+
+[testenv:lint-py3]
+basepython = python3
+skip_install = true
+deps = {[lint]deps}
+commands = {[lint]commands}
+whitelist_externals = {[lint]whitelist_externals}
 
 [testenv:docs]
 basepython = python2.7
 commands =
     sphinx-build -b html -d build/docs/doctrees docs build/docs/html
     sphinx-build -b doctest docs build/docs/doctrees
 deps =
-    .[docs]
+    -cconstraints.txt
+    Sphinx
+
+[testenv:release]
+skip_install = true
+basepython = python2.7
+
+deps =
+    -cconstraints.txt
+    zest.releaser[recommended]
+
+commands =
+    python -V
+    fullrelease --no-input -v