Update pytest to 3.10.1 (the last < 4 release)

See html5lib#429 for
upgrading to >= 4

Author: gsnedders

requirements-test.txt

@@ -9,9 +9,9 @@ tox==3.14.5 \
 flake8==3.7.9 \
     --hash=sha256:45681a117ecc81e870cbf1262835ae4af5e7a8b08e40b944a8a6e6b895914cfb \
     --hash=sha256:49356e766643ad15072a789a20915d3c91dc89fd313ccd71802303fd67e4deca
-pytest==3.2.5 \
-    --hash=sha256:241d7e7798d79192a123ceaf64c602b4d233eacf6d6e42ae27caa97f498b7dc6 \
-    --hash=sha256:6d5bd4f7113b444c55a3bbb5c738a3dd80d43563d063fc42dcb0aaefbdd78b81
+pytest==3.10.1 \
+    --hash=sha256:3f193df1cfe1d1609d4c583838bea3d532b18d6160fd3f55c9447fdca30848ec \
+    --hash=sha256:e246cf173c01169b9617fc07264b7b1316e78d7a650055235d6d897bc80d9660
 coverage==5.0.3 \
     --hash=sha256:15cf13a6896048d6d947bf7d222f36e4809ab926894beb748fc9caa14605d9c3 \
     --hash=sha256:1daa3eceed220f9fdb80d5ff950dd95112cd27f70d004c7918ca6dfc6c47054c \