Temporary fix to get nightly green again

[mattdangerw]

Our segfault appears to do with import order. Importing sentencepiece first, everything is ok, importing tf first, the trainer breaks.

This should be a safe change to get CI green while we look for a longer term solution.

[chenmoneygithub]

thx!

[jbischof]

Short fix is good. Thanks!

I guess this means that someone running a SP-based tokenizer will be prompted to install the lib separately?

[mattdangerw]

I guess this means that someone running a SP-based tokenizer will be prompted to install the lib separately?

We actually don't need the sentencepiece package for tokenization, that is handled by tf-text.

We need sentencepiece for training a "sentencepiece proto", which happens both in our unit testing and the compute_sentence_piece_proto utility. If an end users attempts to call compute_sentence_piece_proto without the package installed, they get an error with instructions on installation.