You can typically see the error messages produced by plug-ins using the
If you'd like to put those messages into a Vim buffer, so that you can copy them to the clipboard from there, you can use the following command:
This uses the
execute() function to capture output of an Ex command, then the expression register
"= to use that in a register context and finally the
:put command to append the contents of that register to the current buffer.
:help "= and
:help :put for more details.