RateLimitFilter: Fix issues with unicode exceptions.
RateLimitFilter: Fix issues with unicode exceptions.

If you call str() on an exception with unicode characters in it, that
will itself throw an exception.

eeshangarg/zulip,brockwhittaker/zulip,verma-varsha/zulip,brockwhittaker/zulip,hackerkid/zulip,amanharitsh123/zulip,amanharitsh123/zulip,kou/zulip,kou/zulip,vaidap/zulip,rht/zulip,showell/zulip,mahim97/zulip,mahim97/zulip,punchagan/zulip,dhcrzf/zulip,jackrzhang/zulip,punchagan/zulip,rishig/zulip,punchagan/zulip,Galexrt/zulip,zulip/zulip,jrowan/zulip,jrowan/zulip,hackerkid/zulip,jackrzhang/zulip,tommyip/zulip,zulip/zulip,andersk/zulip,brainwane/zulip,rishig/zulip,kou/zulip,verma-varsha/zulip,punchagan/zulip,zulip/zulip,jrowan/zulip,vaidap/zulip,Galexrt/zulip,amanharitsh123/zulip,punchagan/zulip,hackerkid/zulip,rht/zulip,kou/zulip,showell/zulip,brainwane/zulip,mahim97/zulip,andersk/zulip,amanharitsh123/zulip,rishig/zulip,timabbott/zulip,synicalsyntax/zulip,vabs22/zulip,shubhamdhama/zulip,showell/zulip,rishig/zulip,showell/zulip,Galexrt/zulip,Galexrt/zulip,brockwhittaker/zulip,brockwhittaker/zulip,dhcrzf/zulip,synicalsyntax/zulip,Galexrt/zulip,kou/zulip,jrowan/zulip,vaidap/zulip,hackerkid/zulip,timabbott/zulip,synicalsyntax/zulip,vabs22/zulip,vaidap/zulip,tommyip/zulip,rishig/zulip,eeshangarg/zulip,rishig/zulip,timabbott/zulip,showell/zulip,andersk/zulip,brainwane/zulip,timabbott/zulip,eeshangarg/zulip,zulip/zulip,synicalsyntax/zulip,tommyip/zulip,rht/zulip,punchagan/zulip,synicalsyntax/zulip,dhcrzf/zulip,vabs22/zulip,eeshangarg/zulip,rishig/zulip,hackerkid/zulip,shubhamdhama/zulip,rht/zulip,showell/zulip,amanharitsh123/zulip,jackrzhang/zulip,shubhamdhama/zulip,jrowan/zulip,vabs22/zulip,jackrzhang/zulip,Galexrt/zulip,mahim97/zulip,eeshangarg/zulip,tommyip/zulip,hackerkid/zulip,hackerkid/zulip,rht/zulip,punchagan/zulip,vaidap/zulip,zulip/zulip,rht/zulip,jrowan/zulip,verma-varsha/zulip,verma-varsha/zulip,kou/zulip,shubhamdhama/zulip,jackrzhang/zulip,mahim97/zulip,showell/zulip,synicalsyntax/zulip,amanharitsh123/zulip,dhcrzf/zulip,shubhamdhama/zulip,vaidap/zulip,zulip/zulip,Galexrt/zulip,jackrzhang/zulip,synicalsyntax/zulip,eeshangarg/zulip,tommyip/zulip,timabbott/zulip,andersk/zulip,dhcrzf/zulip,brockwhittaker/zulip,brainwane/zulip,eeshangarg/zulip,tommyip/zulip,dhcrzf/zulip,timabbott/zulip,shubhamdhama/zulip,vabs22/zulip,verma-varsha/zulip,vabs22/zulip,zulip/zulip,brainwane/zulip,dhcrzf/zulip,kou/zulip,andersk/zulip,shubhamdhama/zulip,jackrzhang/zulip,brainwane/zulip,brainwane/zulip,rht/zulip,mahim97/zulip,timabbott/zulip,andersk/zulip,tommyip/zulip,andersk/zulip,verma-varsha/zulip,brockwhittaker/zulip