@windelbouwman the cpython check fails, because of the version conflict.

I have Python 3.7, in which the float.__doc__ contains Convert a string or number to a floating point number, if possible., but the Travis check uses the Python 3.6 version in which float.__doc__ contains
float(x) -> floating point number\n\nConvert a string or number to a floating point number, if possible.

What version should be chosen here?

For most of the types __doc__ string is different from python 3.7 to 3.6
Please decide that ASAP

I would not test the docstrings and take the latest from python 3.7. This is probably most accurate. Note that we might choose our docstrings from being different (if this means more clear / better) than CPython. The aim of rustpython is not per se 100% compatibility with cpython.

@windelbouwman I will then remove the latest commit.
Would you like to remove all other __doc__ tests (e.g. for bool) in the separate PR?

Done

It would be good to remove too strict tests on doc strings such that they work on both CPython 3.7 and CPython 3.6.