Report combined coverage to codecov (#4225)

tox.ini

@@ -7,6 +7,7 @@ deps =
     mock
     python-subunit
     junitxml
+    coverage
 
     # needed by some of the tests
     lxml
@@ -27,11 +28,15 @@ deps =
 
 setenv =
     PYTHONDONTWRITEBYTECODE = no_byte_code
+    COVERAGE_PROCESS_START = {toxinidir}/.coveragerc
 
 [testenv]
 deps =
     {[base]deps}
 
+whitelist_externals =
+    sh
+
 setenv =
     {[base]setenv}
 
@@ -39,7 +44,9 @@ passenv = *
 
 commands =
     /usr/bin/find "{toxinidir}" -name '*.pyc' -delete
-    "{envbindir}/trial" {env:TRIAL_FLAGS:} {posargs:tests} {env:TOXSUFFIX:}
+    # Add this so that coverage will run on subprocesses
+    sh -c 'echo "import coverage; coverage.process_startup()" > {envsitepackagesdir}/../sitecustomize.py'
+    {envbindir}/coverage run "{envbindir}/trial" {env:TRIAL_FLAGS:} {posargs:tests} {env:TOXSUFFIX:}
 
 [testenv:py27]
 
@@ -101,17 +108,6 @@ usedevelop=true
 [testenv:py36]
 usedevelop=true
 
-
-[testenv:py36-coverage]
-usedevelop=true
-deps =
-    {[base]deps}
-    coverage
-commands =
-    /usr/bin/find "{toxinidir}" -name '*.pyc' -delete
-    python -m coverage run -m twisted.trial {env:TRIAL_FLAGS:} {posargs:tests} {env:TOXSUFFIX:}
-
-
 [testenv:py36-postgres]
 usedevelop=true
 deps =
@@ -146,3 +142,12 @@ deps = towncrier>=18.6.0rc1
 commands =
    python -m towncrier.check --compare-with=origin/develop
 basepython = python3.6
+
+[testenv:codecov]
+skip_install = True
+deps =
+    coverage
+    codecov
+commands =
+    coverage combine
+    codecov -X gcov