Converting large numbers to text causes crash

[lostways]

Explanation of issue

When trying to convert numbers to words in coqui-ai-TTS/TTS/tts/utils/text/english/number_norm.py, numbers with more than 36 digits will cause inflect to throw inflect.NumOutOfRangeError crashing the app.

Reproduction

This script will reproduce the issue:

from TTS.api import TTS

tts = TTS("tts_models/en/ljspeech/tacotron2-DDC").to("cuda")

# big_number = "1" + "0" * 35 # this will work
big_number = "1" + "0" * 36  # this will not work
text = f"The number is {big_number}"
tts.tts_to_file(
    text=text,
    file_path="output.wav",
)

Solution

The solution is to read out numbers with more than 36 digits one digit at a time. This replicates how a human speaker might handle this. For example reading out digits of pi.

Tests

I have added two tests to verify this change. One will convert a number with 35 digits normally and the other will convert a number with 36 digits.

[eginhard]

Thank you for the PR and adding a test as well! It's a bit of an extreme case, but the fix is simple enough.