Merge branch 'branch-coverage'

* branch-coverage:
  Remove one "no cover" pragma
  Configure coverage to use branch measurement
  Use pytest-cov for coverage collection

.coveragerc

@@ -0,0 +1,2 @@
+[run]
+branch = True

prequ/resolver.py

@@ -61,7 +61,7 @@ def __init__(self, constraints, repository, cache=None, prereleases=False, clear
         self.their_constraints = set()
         self.repository = repository
         if cache is None:
-            cache = DependencyCache()  # pragma: no cover
+            cache = DependencyCache()
         self.dependency_cache = cache
         self.prereleases = prereleases
         self.clear_caches = clear_caches

tox.ini

@@ -6,15 +6,13 @@ deps =
     piplatest: pip
     pip8: pip~=8.0
     pip9: pip~=9.0
-    coverage
     pytest
+    pytest-cov
     pyyaml
 commands =
     pip --version
-    python -m coverage run --source prequ -m pytest \
+    py.test --cov=prequ --cov-config={toxinidir}/.coveragerc \
         --strict --doctest-modules {posargs:tests/ prequ/}
-    python -m coverage report -m
-    python -m coverage html
 
 [testenv:flake8]
 basepython = python2.7