test_auth_backends: Move ResponseMock earlier in the file.
test_auth_backends: Move ResponseMock earlier in the file.

We're going to be using this in the GitHub auth backend as well.

dhcrzf/zulip,andersk/zulip,synicalsyntax/zulip,zulip/zulip,kou/zulip,kou/zulip,synicalsyntax/zulip,showell/zulip,rht/zulip,tommyip/zulip,showell/zulip,kou/zulip,zulip/zulip,brainwane/zulip,hackerkid/zulip,tommyip/zulip,rishig/zulip,punchagan/zulip,timabbott/zulip,eeshangarg/zulip,zulip/zulip,shubhamdhama/zulip,kou/zulip,dhcrzf/zulip,punchagan/zulip,rht/zulip,brainwane/zulip,shubhamdhama/zulip,zulip/zulip,tommyip/zulip,zulip/zulip,synicalsyntax/zulip,zulip/zulip,jackrzhang/zulip,rht/zulip,rht/zulip,andersk/zulip,jackrzhang/zulip,showell/zulip,tommyip/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,andersk/zulip,rishig/zulip,showell/zulip,hackerkid/zulip,hackerkid/zulip,jackrzhang/zulip,brainwane/zulip,rishig/zulip,rht/zulip,shubhamdhama/zulip,brainwane/zulip,dhcrzf/zulip,eeshangarg/zulip,jackrzhang/zulip,jackrzhang/zulip,tommyip/zulip,showell/zulip,synicalsyntax/zulip,timabbott/zulip,shubhamdhama/zulip,shubhamdhama/zulip,kou/zulip,punchagan/zulip,rishig/zulip,punchagan/zulip,andersk/zulip,tommyip/zulip,hackerkid/zulip,andersk/zulip,timabbott/zulip,rht/zulip,kou/zulip,eeshangarg/zulip,brainwane/zulip,timabbott/zulip,andersk/zulip,timabbott/zulip,synicalsyntax/zulip,hackerkid/zulip,andersk/zulip,rishig/zulip,brainwane/zulip,timabbott/zulip,showell/zulip,dhcrzf/zulip,rht/zulip,rishig/zulip,shubhamdhama/zulip,dhcrzf/zulip,dhcrzf/zulip,synicalsyntax/zulip,punchagan/zulip,punchagan/zulip,timabbott/zulip,synicalsyntax/zulip,jackrzhang/zulip,jackrzhang/zulip,shubhamdhama/zulip,rishig/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,tommyip/zulip,showell/zulip,zulip/zulip,kou/zulip,eeshangarg/zulip,brainwane/zulip,dhcrzf/zulip