<NME> test-requirements.txt
<BEF> factory-boy>=2.4
mock==2.0.0; python_version < '3.3'
httmock==1.2.5
tox
asynctest

<MSG> Make dependency to argon2 optional (#1701)


<DFF> @@ -1,3 +1,4 @@
+argon2-cffi>=16.1.0
 factory-boy>=2.4
 mock==2.0.0; python_version < '3.3'
 httmock==1.2.5

Make dependency to argon2 optional (#1701)