How to resolve Python package depencencies with pipenv?

Question

I am using pipenv to handle a Python package dependencies.

The Python package is using two packages (named pckg1 and pckg2) that relies on

Answer 1

I have the similar issue with google-cloud-core.

$ pipenv lock
Locking [dev-packages] dependencies…
Locking [packages] dependencies…

Warning: Your dependencies could not be resolved. You likely have a mismatch in your sub-dependencies.
  First try clearing your dependency cache with $ pipenv lock --clear, then try the original command again.
 Alternatively, you can use $ pipenv install --skip-lock to bypass this mechanism, then run $ pipenv graph to inspect the situation.
  Hint: try $ pipenv lock --pre if it is a pre-release dependency.
Could not find a version that matches google-cloud-core<0.29dev,<0.30dev,>=0.28.0,>=0.29.0
Tried: 0.20.0, 0.20.0, 0.21.0, 0.21.0, 0.22.0, 0.22.0, 0.22.1, 0.22.1, 0.23.0, 0.23.0, 0.23.1, 0.23.1, 0.24.0, 0.24.0, 0.24.1, 0.24.1, 0.25.0, 0.25.0, 0.26.0, 0.26.0, 0.27.0, 0.27.0, 0.27.1, 0.27.1, 0.28.0, 0.28.0, 0.28.1, 0.28.1, 0.29.0, 0.29.0
There are incompatible versions in the resolved dependencies.

It was solved by

1. rm -rf Pipfile.lock
2. pipenv update