apply @gforcada 's recommendations

CHANGES.rst

@@ -14,7 +14,7 @@ New features:
 
 Bug fixes:
 
-- Code Cleanup and enforcing Code Convertions
+- Code Cleanup and enforcing Code Conversions
   [loechel]
 
 

constrains.txt

@@ -0,0 +1,33 @@
+configparser==3.5.0
+cssselect==1.0.1
+enum-compat==0.0.2
+enum34==1.1.6
+flake8==3.4.1
+flake8-blind-except==0.1.1
+flake8-coding==1.3.0
+flake8-commas==0.4.3
+flake8-debugger==1.4.0
+flake8-deprecated==1.2.1
+flake8-html==0.4.0
+flake8-isort==2.2.1
+flake8-pep3101==1.1
+flake8-polyfill==1.0.1
+flake8-print==2.0.2
+flake8-quotes==0.11.0
+flake8-strict==0.1.4
+flake8-string-format==0.2.3
+flake8-todo==0.7
+FormEncode==1.3.1
+future==0.16.0
+isort==4.2.15
+Jinja2==2.9.6
+lxml==3.8.0
+MarkupSafe==1.0
+mccabe==0.6.1
+pycodestyle==2.3.1
+pyflakes==1.5.0
+Pygments==2.2.0
+repoze.xmliter==0.6
+six==1.10.0
+testfixtures==5.1.1
+WebOb==1.7.3

lib/diazo/runtrace.py

@@ -87,7 +87,7 @@ def generate_debug_html(
     """Generate an HTML node with debug info"""
     def newElement(tag, content, **kwargs):
         n = etree.Element(tag, **kwargs)
-        if hasattr(content, 'tag'):
+        if getattr(content, 'tag', None):
             n.append(content)
         else:
             n.text = content

lib/diazo/wsgi.py

@@ -312,7 +312,7 @@ def __call__(self, environ, start_response):
                 # Headers should be left intact
                 return response(environ, start_response)
         finally:
-            if hasattr(response.app_iter, 'close'):
+            if getattr(response.app_iter, 'close', None):
                 response.app_iter.close()
 
         self.reset_headers(response)

tox.ini

@@ -10,8 +10,8 @@ envlist =
     py35,
     py36,
     docs,
-    isort,
-    flake8
+    lint-py2,
+    lint-py3,
     coverage-report,
 
 [testenv]
@@ -28,6 +28,7 @@ setenv =
     COVERAGE_FILE=.coverage.{envname}
 
 deps =
+    -cconstrains.txt
     pdbpp
     pytest
     pytest-cov
@@ -40,36 +41,34 @@ whitelist_externals =
 
 [testenv:coverage-report]
 basepython = python2.7
-deps = coverage
+skip_install = true
+
+deps =
+    -cconstrains.txt
+    coverage
 
 setenv =
     COVERAGE_FILE=.coverage
 
-skip_install = true
-
 commands =
     coverage erase
     coverage combine
     coverage report
     coverage html
     coverage xml
 
-[testenv:isort]
-basepython = python2.7
-deps = isort
-commands =
-    #isort --check-only --recursive {toxinidir}/lib
-    isort --check-only --recursive {toxinidir}/lib
-
 [testenv:isort-apply]
 basepython = python2.7
+skip_install = true
 deps = isort
 commands =
     isort --apply --recursive {toxinidir}/lib
 
-[testenv:flake8]
-basepython = python2.7
+[lint]
+skip_install = true
+
 deps =
+    -cconstrains.txt
     flake8
     # helper to generate HTML reports:
     flake8-html
@@ -81,36 +80,51 @@ deps =
     flake8-isort
     flake8-pep3101
 #    flake8-plone-api
-#    flake8-plone-hasattr
+    flake8-plone-hasattr
     flake8-print
     flake8-quotes
     flake8-string-format
     flake8-todo
     flake8_strict
+    isort
 
 commands =
     mkdir -p {toxinidir}/reports/flake8
+    #isort --check-only --recursive {toxinidir}/src
     #- flake8 --format=html --htmldir={toxinidir}/reports/flake8 --doctests src tests setup.py
     #flake8 src tests setup.py --doctests
+    isort --check-only --recursive {toxinidir}/lib
     - flake8 --format=html --htmldir={toxinidir}/reports/flake8 --doctests lib setup.py
     flake8 lib setup.py --doctests
 
 whitelist_externals =
     mkdir
 
+[testenv:lint-py2]
+basepython = python2
+deps = {[lint]deps}
+commands = {[lint]commands}
+
+[testenv:lint-py3]
+basepython = python3
+deps = {[lint]deps}
+commands = {[lint]commands}
+
 [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 =
+    -cconstrains.txt
     Sphinx
 
 [testenv:release]
 skip_install = true
 basepython = python2.7
 
 deps =
+    -cconstrains.txt
     zest.releaser[recommended]
 
 commands =