Simplify coverage handling

- Always install coverage tools.
- Show coverage if all tests pass.
- Less conditional code.

Makefile

@@ -30,11 +30,6 @@ PYTEST_ARGS =
 
 TEST_EXTRA_PACKAGES =
 
-ifeq ($(COVERAGE), true)
-	TEST_EXTRA_PACKAGES += pytest-cov
-	PYTEST_ARGS += --cov-config .coveragerc --cov vdirsyncer
-endif
-
 ifeq ($(ETESYNC_TESTS), true)
 	TEST_EXTRA_PACKAGES += git+https://github.com/etesync/journal-manager@v0.5.2
 	TEST_EXTRA_PACKAGES += django djangorestframework==3.8.2 wsgi_intercept drf-nested-routers

setup.cfg

@@ -3,7 +3,12 @@ universal = 1
 
 [tool:pytest]
 norecursedirs = tests/storage/servers/*
-addopts = --tb=short
+addopts =
+  --tb=short
+  --cov-config .coveragerc
+  --cov=vdirsyncer
+  --cov-report=term-missing
+  --no-cov-on-fail
 
 [flake8]
 # E731: Use a def instead of lambda expr

test-requirements.txt

@@ -1,4 +1,5 @@
 hypothesis>=5.0.0
 pytest
+pytest-cov
 pytest-localserver
 pytest-subtesthack