install: Improve some error output for common errors.
install: Improve some error output for common errors.

This uses `set +x` to hide the `echo` output, and then sets the font
color to red.

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