[Fix] missing prophet/catboost/lightgbm library should not prevent use of others models

[madtoinou]

Fixes ##1272 and #1217.

Summary

Exception handling in models/__init__.py to display warning message when trying to import models depending on uninstalled external libraries. The logger will display a warning message, linking to the INSTALL.md file when relevant.

Other Information

• The unavailable models are replaced by dummy class with explicit name so that the user should realize that the import failed even if the warnings are ignored.
• I had to add similar logic in regression_model.py can eventually depend on the CatBoostRegressor.
• The exception handling was not extended to the tests so that they remain a reliable way to verify that the local install is correct.

[codecov-commenter]

Codecov Report

Base: 93.89% // Head: 93.86% // Decreases project coverage by -0.02% ⚠️

Coverage data is based on head (a131304) compared to base (4dc4930).
Patch coverage: 50.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1360      +/-   ##
==========================================
- Coverage   93.89%   93.86%   -0.03%     
==========================================
  Files          78       78              
  Lines        8520     8511       -9     
==========================================
- Hits         8000     7989      -11     
- Misses        520      522       +2     

Impacted Files	Coverage Δ
darts/models/forecasting/regression_model.py	97.53% <50.00%> (-0.69%)	⬇️
darts/timeseries.py	92.34% <0.00%> (-0.06%)	⬇️
...arts/models/forecasting/torch_forecasting_model.py	87.08% <0.00%> (-0.06%)	⬇️
darts/models/forecasting/block_rnn_model.py	98.24% <0.00%> (-0.04%)	⬇️
darts/models/forecasting/nhits.py	99.27% <0.00%> (-0.01%)	⬇️

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[hrzn]

LGTM 💯

[chartsengrafs]

I am still getting this error with =0.23.1

`/opt/conda/envs/myenv/lib/python3.7/site-packages/darts/models/init.py in
10 # Forecasting
11 from darts.models.forecasting.arima import ARIMA
---> 12 from darts.models.forecasting.auto_arima import AutoARIMA
13 from darts.models.forecasting.baselines import NaiveDrift, NaiveMean, NaiveSeasonal
14 from darts.models.forecasting.exponential_smoothing import ExponentialSmoothing

/opt/conda/envs/myenv/lib/python3.7/site-packages/darts/models/forecasting/auto_arima.py in
9
10 from darts.logging import get_logger, raise_if
---> 11 from darts.models.forecasting.forecasting_model import (
12 FutureCovariatesLocalForecastingModel,
13 )

ImportError: cannot import name 'FutureCovariatesLocalForecastingModel' from 'darts.models.forecasting.forecasting_model' (/opt/conda/envs/myenv/lib/python3.7/site-packages/darts/models/forecasting/forecasting_model.py)`

[hrzn]

Mmhh that's weird. FutureCovariatesLocalForecastingModel should be available. Could you maybe try deleting & recreating your virtual environment and reinstalling darts from scratch?

[WangariKimotho]

hi, also getting the error with darts version 0.23.1:
ImportError: cannot import name 'TFTModel' from 'darts.models' ([/home/ri/anaconda3/envs/ml_ds/lib/python3.10/site-packages/darts/models/init.py])

[WangariKimotho]

hi, also getting the error with darts version 0.23.1: ImportError: cannot import name 'TFTModel' from 'darts.models' ([/home/ri/anaconda3/envs/ml_ds/lib/python3.10/site-packages/darts/models/init.py])

resolved by "from darts.models.forecasting.tft_model import TFTModel" and "pip install lightning"