Detect CPORT header in SAS files
Refers https://github.com/pandas-dev/pandas/issues/15825 . Doesn't fix the issue (might be unfixable), but gives a more helpful warning.

lgtm. @bashtage if any comments. I just deleted most of the CPT binary to cut down on wasted space - unit tests still pass. > I just deleted most of the CPT binary to cut down on wasted space - unit tests still pass.

If you want to keep the shortened CPT file (and why not), you should be sure to rebase and squash to a single commit so that any history is removed from the commits. > > I just deleted most of the CPT binary to cut down on wasted space - unit tests still pass.
> 
> If you want to keep the shortened CPT file (and why not), you should be sure to rebase and squash to a single commit so that any history is removed from the commits.

Oh yeah, my bad! Done. thanks @lordgrenville 