--html-to-org-with-pandoc reports error from pandoc instead of "Pandoc failed".

[c1-g]

Here is the patch that makes the process from pandoc replace the
buffer string with its error message and show it throught the capture
buffer.

This is intended to be used to debug #42.

[alphapapa]

Thanks, but this patch would leave the temp file on disk. You should probably use unwind-protect.

[c1-g]

@alphapapa Hi, I added unwind-protect like you requested. Sorry I took so long to reply.

[alphapapa]

Thanks for your patience. I squashed, rebased, updated the changelog, and merged.