Document markers used by pytest.

This may or may not become a requirement in the future.

Author: QuLogic

pytest.ini

@@ -1,6 +1,12 @@
 [pytest]
 norecursedirs = .git build ci dist doc extern lib/mpl_examples release tools unit venv
 python_files = test_*.py
+
+markers =
+    backend: Set alternate Matplotlib backend temporarily.
+    network: Mark a test that uses the network.
+    style: Set alternate Matplotlib style temporarily.
+
 pep8ignore =
     * E111 E114 E115 E116 E121 E122 E123 E124 E125 E126 E127 E128 E129 E131 E226 E240 E241 E242 E243 E244 E245 E246 E247 E248 E249 E265 E266 E704 W503