manage.py: Print CommandError exceptions cleanly.
manage.py: Print CommandError exceptions cleanly.

Django, by default, prints these exceptions as a giant traceback,
which is really ugly and scary to sysadmins.  We really just want to
print the error message to stdout for convenient viewing by the user.

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