Human readable name not used in parameter error messages

[gar1t]

I'm getting error messages that look like this:

Usage: guild info [OPTIONS] PACKAGE
Try "guild info --help" for help.

Error: Missing argument "package".

IMO the last line should read Missing argument PACKAGES - "packages" is not reflected in the usage.

I believe the issue is here (and similar patterns in exceptions.py):

https://github.com/pallets/click/blob/master/click/exceptions.py#L121

where self.param.opts short-circuits the use of the human readable name, which would use metavar as expected.

[cdunklau]

This looks like a dupe of #598

[LokiHokie]

Fixed #709