Bump pytest from 4.2.0 to 4.2.1 in /requirements

Bumps [pytest](https://github.com/pytest-dev/pytest) from 4.2.0 to 4.2.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@4.2.0...4.2.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot-support

requirements/dev.txt

@@ -1,8 +1,8 @@
 # Dependencies needed only for development/testing.
 
-pytest==4.2.0 \
-    --hash=sha256:6ac6d467d9f053e95aaacd79f831dbecfe730f419c6c7022cb316b365cd9199d \
-    --hash=sha256:65aeaa77ae87c7fc95de56285282546cfa9c886dc8e5dc78313db1c25e21bc07
+pytest==4.2.1 \
+    --hash=sha256:80cfd9c8b9e93f419abcc0400e9f595974a98e44b6863a77d3e1039961bfc9c4 \
+    --hash=sha256:c2396a15726218a2dfef480861c4ba37bd3952ebaaa5b0fede3fc23fddcd7f8c
 
 django-debug-toolbar==1.11 \
     --hash=sha256:c2b0134119a624f4ac9398b44f8e28a01c7686ac350a12a74793f3dd57a9eea0 \