fastpitch_finetuning.ipynb does not work from scratch
Hi all. 

The tutorial https://github.com/NVIDIA/NeMo/blob/main/tutorials/tts/FastPitch_Finetuning.ipynb does not work from scratch.

First, I have to replace NeMo for NVIDIA in the first setup cell for enable it to run:

```
!python -m pip install git+https://github.com/NeMo/NeMo.git@$BRANCH#egg=nemo_toolkit[all]
```

for

```
!python -m pip install git+https://github.com/NVIDIA/NeMo.git@$BRANCH#egg=nemo_toolkit[all]
```

Then, I got the following error in the 11th cell:

First commands of the cell:

```
new_speaker_id = 6097
duration_mins = 5
mixing = False
original_speaker_id = "ljspeech"

_ ,last_ckpt = get_best_ckpt("./", new_speaker_id, duration_mins, mixing, original_speaker_id)
print(last_ckpt)
```

Error:

```
AttributeError                            Traceback (most recent call last)
[/usr/local/lib/python3.7/dist-packages/torch/serialization.py](https://localhost:8080/#) in _check_seekable(f)
    307     try:
--> 308         f.seek(f.tell())
    309         return True

AttributeError: 'NoneType' object has no attribute 'seek'

During handling of the above exception, another exception occurred:

AttributeError                            Traceback (most recent call last)
8 frames
[/usr/local/lib/python3.7/dist-packages/torch/serialization.py](https://localhost:8080/#) in raise_err_msg(patterns, e)
    302                                 + " Please pre-load the data into a buffer like io.BytesIO and"
    303                                 + " try to load from it instead.")
--> 304                 raise type(e)(msg)
    305         raise e
    306 

AttributeError: 'NoneType' object has no attribute 'seek'. You can only torch.load from a file that is seekable. Please pre-load the data into a buffer like io.BytesIO and try to load from it instead.
```

Best,