warn if both `tensorboard` and `tb-nightly` pip packages are installed

This is a common source of inscrutable errors, because pip will happily install both pip packages even though they both ship the tensorboard python package [1], and in doing so the second one will overwrite any files from the first one: https://github.com/pypa/pip/issues/4625. This means you can easily end up with a garbled frankentensorboard package (and it gets even worse if you uninstall one of them but not both of them, since then you get a frankentensorboard with a lot of vital organs removed).

Until pip fixes this mess, it’s a fact of life, but we can at least try to warn users about this pitfall ourselves.

[1] It’s colloquial to call both of these packages, so I’m prefixing to avoid confusion. See also https://github.com/pypa/packaging.python.org/issues/106

[wchargin]

Quick update: TensorBoard itself doesn’t warn you about this failure mode, but our self-diagnosis script does: https://raw.githubusercontent.com/tensorflow/tensorboard/master/tensorboard/tools/diagnose_tensorboard.py

If you run it, you’ll get a message like:

WARNING: conflicting installations: ['tb-nightly', 'tensorboard']

Suggestion: Fix conflicting installations

Conflicting package installations found. Depending on the order of installations and uninstallations, behavior may be undefined. Please uninstall ALL versions of TensorFlow and TensorBoard, then reinstall ONLY the desired version of TensorFlow, which will transitively pull in the proper version of TensorBoard. (If you use TensorBoard without TensorFlow, just reinstall the appropriate version of TensorBoard directly.)

Namely:

pip uninstall tb-nightly tensorboard
pip install tensorflow  # or `tensorflow-gpu`, or `tf-nightly`, ...

It would still be nice to do this at runtime, too, as described in this issue.

[janosh]

…but it’s a good point that at least for now it’s easy for users to arrive in this state by following our own instructions.

Exactly. This happened to me. Didn’t realize for quite some time that I had an old TB installation lying around.