Bump pytest from 4.2.0 to 4.2.1 (#329)

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](https://github.com/pytest-dev/pytest/compare/4.2.0...4.2.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements/py27-tests.txt

@@ -2,7 +2,7 @@ mock==2.0.0
 mozlog==4.0
 pyfxa==0.6.0
 pypom==2.2.0
-pytest==4.2.0
+pytest==4.2.1
 pytest-fxa==1.4.0
 pytest-metadata==1.8.0
 pytest-selenium==1.15.1

requirements/py36-tests.txt

@@ -1,7 +1,7 @@
 mock==2.0.0
 pyfxa==0.6.0
 pypom==2.2.0
-pytest==4.2.0
+pytest==4.2.1
 pytest-fxa==1.4.0
 pytest-metadata==1.8.0
 pytest-selenium==1.15.1