Fix coverage measurement

Now tox -e coverage correctly reports 50%.

.coveragerc

@@ -0,0 +1,9 @@
+[run]
+source = z3c.recipe.tag
+parallel = true
+
+[paths]
+source =
+    src/
+    .tox/*/lib/python*/site-packages/
+    .tox/pypy*/site-packages/

setup.cfg

@@ -0,0 +1,4 @@
+[flake8]
+doctests = yes
+# provided to doctests by buildoutSetUp()
+builtins = write, system, cat, join

src/z3c/recipe/tag/__init__.py

@@ -219,10 +219,10 @@ def build_tags(args=None):
     import paver.easy
 except ImportError:
     HAS_PAVER = False
-else:
+else:  # pragma: nocover
     HAS_PAVER = True
 
-if HAS_PAVER:
+if HAS_PAVER:  # pragma: nocover
     @paver.easy.task
     @paver.easy.consume_args
     def tags(args):

src/z3c/recipe/tag/tests.py

@@ -10,10 +10,6 @@
 def doctest_tags_recipe():
     """Test for z3c.recipe.tag
 
-        >>> write = write  # noqa: F821 (undefined name)
-        >>> system = system  # noqa: F821 (undefined name)
-        >>> cat = cat  # noqa: F821 (undefined name)
-        >>> join = join  # noqa: F821 (undefined name)
         >>> write('buildout.cfg',
         ... '''
         ... [buildout]
@@ -81,7 +77,7 @@ def tearDown(test):
     (re.compile("Not found: .*buildouttests/[a-zA-Z0-9.]+/\n"), ''),
 ])
 
-if os.getenv('RUNNING_UNDER_TOX') or os.getenv('TRAVIS'):
+if os.getenv('RUNNING_UNDER_TOX') or os.getenv('TRAVIS'):  # pragma: nocover
     # tox installs our test dependencies into the virtualenv,
     # and zc.buildout has no site isolation, so it finds them there,
     # so it doesn't add them to sys.path in the generated scripts

tox.ini

@@ -17,9 +17,12 @@ extras = test
 
 [testenv:coverage]
 basepython = python3.7
+setenv =
+    COVERAGE_PROCESS_START={toxinidir}/.coveragerc
 commands =
     coverage run -m zope.testrunner --test-path=src []
-    coverage report --fail-under=86
+    coverage combine
+    coverage report -m --fail-under=50
 deps =
     coverage