Why is python setup.py saying invalid command 'bdist_wheel' on Travis CI?

The error message "invalid command 'bdist_wheel'" occurs when the "bdist_wheel" module is not installed. This module is required to build wheel distributions, which are a newer format for distributing Python packages.

You can resolve this issue by installing the wheel package, which provides the "bdist_wheel" module. You can do this by adding the following line to your requirements.txt file:

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wheel

Or you can install it via pip:

pip install wheel

You may also want to add this command to the install step of your .travis.yml file:

install:
- pip install wheel

This will ensure that wheel is installed before the python setup.py command is run.