csvjoin does not pass through single file

Created by: kundor

The help text for csvjoin states

 positional arguments:
  FILE                  The CSV files to operate on. If only one is specified,
                        it will be copied to STDOUT.

This doesn't seem to be true, however. If I run csvjoin with a single file argument, it gives me:

csvjoin: error: You must specify at least two files to join.

I'd prefer if the documented behavior was true. I have a little script which combines grades in CSV files using csvjoin and csvcut to combine different assignments in the same section, followed by csvstack for multiple sections. If there happens to just be one assignment from each section, only one file would be given to csvjoin and it refuses to pass it through, so I have to put a special case in my script, which is annoying.

This is with csvkit version 1.0.3 and Python 3.6.3.