Enable coverage reporting via codecov

.coveragerc

@@ -0,0 +1,5 @@
+[run]
+branch = 1
+# NOTE: cannot use package easily, without chdir (https://github.com/nedbat/coveragepy/issues/268).
+source = paste/,tests/
+parallel = 1

.travis.yml

@@ -7,14 +7,22 @@ script:
 matrix:
     include:
         - python: 2.7
-          env: TOXENV=py27
+          env: TOXENV=py27-coverage
         - python: 3.5
-          env: TOXENV=py35
+          env: TOXENV=py35-coverage
         - python: 3.6
-          env: TOXENV=py36
+          env: TOXENV=py36-coverage
         - python: 3.7
-          env: TOXENV=py37
+          env: TOXENV=py37-coverage
           dist: xenial
           sudo: true
         - python: pypy
-          env: TOXENV=pypy
+          env: TOXENV=pypy-coverage
+
+after_success:
+  - |
+    flags=${TOXENV%-coverage}
+    if [[ "$flags" != "$TOXENV" ]]; then
+      .tox/$TOXENV/bin/coverage xml
+      bash <(curl -s https://codecov.io/bash) -Z -X gcov -X search -X xcode -X fix -X coveragepy -f coverage.xml -F "$flags"
+    fi

tox.ini

@@ -2,8 +2,13 @@
 envlist = py27, py35, py36, py37, pypy
 
 [testenv]
+# For performance, but also for using "source" with coveragepy (https://github.com/nedbat/coveragepy/issues/268).
+usedevelop = True
 deps =
     pytest
-    pytest-cov
+    coverage: coverage
+    coverage: pytest-cov
+setenv =
+    coverage: PYTEST_ADDOPTS=--cov --cov-report=term-missing
 commands =
     py.test {posargs}