<NME> test-requirements.txt
<BEF> argon2-cffi>=16.1.0
factory-boy<=2.12.0
httmock==1.4.0
testfixtures==6.15.0
tox
asynctest

<MSG> Bump testfixtures from 6.15.0 to 6.16.0

Bumps [testfixtures](https://github.com/Simplistix/testfixtures) from 6.15.0 to 6.16.0.
- [Release notes](https://github.com/Simplistix/testfixtures/releases)
- [Changelog](https://github.com/Simplistix/testfixtures/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/Simplistix/testfixtures/compare/6.15.0...6.16.0)

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
<DFF> @@ -1,6 +1,6 @@
 argon2-cffi>=16.1.0
 factory-boy<=2.12.0
 httmock==1.4.0
-testfixtures==6.15.0
+testfixtures==6.16.0
 tox
 asynctest

Bump testfixtures from 6.15.0 to 6.16.0