Add a coverage job for Python 3 to tox

.coveragerc

@@ -1,4 +1,4 @@
 [run]
 branch = True
 omit =
-  pip/_vendor/*
+  src/pip/_vendor/*

.gitignore

@@ -19,6 +19,7 @@ docs/build/
 
 # Unit test / coverage reports
 .tox/
+htmlcov/
 .coverage
 .coverage.*
 .cache

dev-requirements.txt

@@ -2,6 +2,7 @@ freezegun
 pretend
 pytest
 pytest-catchlog
+pytest-cov
 pytest-rerunfailures
 pytest-timeout
 pytest-xdist

tox.ini

@@ -14,6 +14,10 @@ commands = py.test --timeout 300 []
 install_command = python -m pip install {opts} {packages}
 usedevelop = True
 
+[testenv:coverage-py3]
+basepython = python3
+commands = py.test --timeout 300 --cov=pip --cov-report=term-missing --cov-report=xml --cov-report=html tests/unit {posargs}
+
 [testenv:docs]
 deps = -r{toxinidir}/docs-requirements.txt
 basepython = python2.7