Why does this CURL (shell/terminal) command fail to execute?
You should add -v or --verbose option to your curl command to get detailed debugging information printed on your terminal to help you trace source of the problem.
As per man curl:
-v, --verboseMakes curl verbose during the operation. Useful for debugging and seeing what's going on "under the hood". A line starting with
'>'means "header data" sent by curl,'<'means "header data" received by curl that is hidden in normal cases, and a line starting with'*'means additional info provided by curl.