coverage: use modules for source

This should increase coverage for subprocesses, where previously
`source` paths were used only from the config file, but not the initial
`--source` argument.

.coveragerc

@@ -1,4 +1,9 @@
 [run]
-source = _pytest,testing
+source = pytest,_pytest,testing/
 parallel = 1
 branch = 1
+
+[paths]
+source = src/
+  .tox/*/lib/python*/site-packages/
+  .tox\*\Lib\site-packages\

.travis.yml

@@ -84,7 +84,7 @@ before_script:
     if [[ "$PYTEST_NO_COVERAGE" != 1 ]]; then
       export COVERAGE_FILE="$PWD/.coverage"
       export COVERAGE_PROCESS_START="$PWD/.coveragerc"
-      export _PYTEST_TOX_COVERAGE_RUN="coverage run --source {envsitepackagesdir}/_pytest/,{toxinidir}/testing -m"
+      export _PYTEST_TOX_COVERAGE_RUN="coverage run -m"
       export _PYTEST_TOX_EXTRA_DEP=coverage-enable-subprocess
     fi
 

scripts/prepare-coverage.bat

@@ -2,7 +2,7 @@ REM scripts called by AppVeyor to setup the environment variables to enable cove
 if not defined PYTEST_NO_COVERAGE (
     set "COVERAGE_FILE=%CD%\.coverage"
     set "COVERAGE_PROCESS_START=%CD%\.coveragerc"
-    set "_PYTEST_TOX_COVERAGE_RUN=coverage run --source {envsitepackagesdir}/_pytest/,{toxinidir}/testing -m"
+    set "_PYTEST_TOX_COVERAGE_RUN=coverage run -m"
     set "_PYTEST_TOX_EXTRA_DEP=coverage-enable-subprocess"
     echo Coverage setup completed
 ) else (