Error immediately when no wheel is available for a package

[travishathaway]

What's the idea?

For PyPI packages that don't have wheel files and just consist of source distributions (e.g. https://pypi.org/simple/ach/), when you run conda pypi install <package>, the conversion just loops until the maximum limit (20).

Steps to reproduce

# Just use a package that only has a source distribution (i.e. ".tar.gz")
conda pypi install ach

What should happen instead?

conda pypi should be more intelligent and try to detect this. When this state is detected, the program should exit with a meaningful error message to the user (e.g. "A wheel file is a not available for this package and cannot be used with conda pypi)

[dholth]

A couple of other variations:

• Only an older version of a package has wheels
• Package has binary wheels and pure-Python wheels, but the pure-Python ones are worse (example: SQLAlchemy)