Merge ~cjwatson/lazr.restful:coverage into lazr.restful:main

[Colin Watson]

Add coverage testing

[Jürgen Gmach (jugmac00)]

Thanks a lot! Not sure what bit I was missing.

Coverage is and remains magic :-)

The current output looks like...

```
.tox/coverage/lib/python3.8/site-packages/lazr/restful/tests/test_etag.py 118 9 92% 47, 52-56, 64-67, 74-89, 100-120
.tox/coverage/lib/python3.8/site-packages/lazr/restful/tests/test_navigation.py 69 1 99% 58
.tox/coverage/lib/python3.8/site-packages/lazr/restful/tests/test_utils.py 116 0 100%
.tox/coverage/lib/python3.8/site-packages/lazr/restful/tests/test_webservice.py 525 5 99% 119, 873, 1011, 1032, 1061
.tox/coverage/lib/python3.8/site-packages/lazr/restful/utils.py 193 6 97% 152, 306, 402, 451-459
.tox/coverage/lib/python3.8/site-packages/lazr/restful/wsgi.py 36 18 50% 32-33, 36-50, 57-61, 66-67
--------------------------------------------------------------------------------------------------------------------------------------
TOTAL 6636 434 93%
__________________________________________________________________________________ summary ___________________________________________________________________________________
  coverage: commands succeeded
  congratulations :)
```

Usually, you would add a `[coverage:paths]` section, and add something like...

```
[coverage:paths]
source =
    src
    .tox/*/site-packages
```

and then you'd get a nicer output (ie src/lazr/restful/.../test_function.py ...), but for reasons unknown it does not work here, at least for me.

review: Approve

[Colin Watson (cjwatson)]

Right, I tried `coverage:paths` too and couldn't see why it wasn't working. Odd, but I didn't want to spend too much time on it, and this at least works.

diff --git a/.gitignore b/.gitignore
index ee6caa6..d2b3b94 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,10 +1,12 @@
 *.egg-info
 *.pyc
+.coverage
 .DS_Store
 .tox
 bin
 build
 dist
+htmlcov
 MANIFEST
 src/lazr/restful/docs/_build
 TAGS
diff --git a/tox.ini b/tox.ini
index c191378..4b07cac 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,6 +8,7 @@ envlist =
     py39
     py310
     docs
+    coverage
 
 [testenv]
 deps =
@@ -31,6 +32,22 @@ deps =
 commands =
     sphinx-build -b html -d src/lazr/restful/docs/_build/doctrees src/lazr/restful/docs src/lazr/restful/docs/_build/html
 
+[testenv:coverage]
+basepython = python3
+deps =
+    .[test,xml]
+    zope.testrunner
+    coverage
+commands =
+    coverage erase
+    coverage run -m zope.testrunner --test-path src --tests-pattern ^tests {posargs}
+    coverage html
+    coverage report -m --fail-under=93
+
+[coverage:run]
+source = lazr.restful
+omit = */docs/conf.py
+
 [flake8]
 ignore =
     # incompatible with black