Switch to coverage_python_version as suggested by @mgedmin.

.coveragerc

@@ -1,6 +1,7 @@
 [run]
 branch = True
 source = z3c.etestbrowser
+plugins = coverage_python_version
 
 [report]
 precision = 2

.travis.yml

@@ -14,7 +14,7 @@ matrix:
       after_success:
 install:
   - pip install -U pip setuptools zope.testrunner
-  - pip install -U coveralls coverage
+  - pip install -U coveralls coverage coverage-python-version
   - pip install -U -e ".[test]"
 script:
   - coverage run -m zope.testrunner --test-path=src --auto-color

src/z3c/etestbrowser/browser.py

@@ -75,8 +75,8 @@ def etree(self):
             match = RE_CHARSET.match(content_type)
             if match is not None:
                 charset = match.groups()[0]
-                if six.PY2:  # pragma: no cover
-                    content = content.decode(charset)  # pragma: no cover
+                if six.PY2:  # pragma: PY2
+                    content = content.decode(charset)  # pragma: PY2
             self._etree = lxml.etree.HTML(content)
 
         if self._etree is None:

tox.ini

@@ -16,7 +16,9 @@ basepython = python3.7
 commands =
     coverage run -m zope.testrunner --test-path=src {posargs:--auto-color -vv}
     coverage report --show-missing --fail-under=93
-deps = coverage
+deps =
+    coverage
+    coverage-python-version
 
 [testenv:flake8]
 basepython = python2.7