- removes lockfile copies without version
- enforces that `buildpack.python_version` is always specified (major_pythons['3'] in cases where it could have been falsy before)
- warns when Python version is unspecified, which ensures future reproducibility failures
replaces `.py2` special-case with a general `separate_kernel_env` flag,
currently triggered by requesting Python < 3.7.
Python 3.6 and 3.5 are now treated as Python 2.7
Maybe --clear flag works as part of `pipenv install` now, but code
inspection indicates to me it still don't. This resolves the issue with
the pipenv versions we currently use in tests at least.
The '//' will render to '/' in the Dockerfile that allows the RUN
command to continue on a new line. I initially added a '//' within a
python string on a blank line in order to format things within the
Python file to look potentially nicer, but this is of little importance
and I have now removed it again.
While trying to update the buildpack for changes in the PR that added
support for using a .binder directory I regressed to faulty logic. This
PR fixes that, adds some comments to avoid it, and get's things right
enough to manage to get the tests to succeed.