Repository: pytorch
Issue: `enumerate_support` for continuous distributions
Labels: module: distributions,triaged

### 🐛 Describe the bug

As expected, `.enumerate_support()` fails on continuous distributions and returns a NotImplementedError.

```python
import torch
dist = torch.distributions
normal = dist.Normal(loc = 0., scale = 1.)
normal.enumerate_support()
```

```python
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
Input In [46], in <module>
      1 ### 
----> 3 normal.enumerate_support()

File ~/miniforge3/lib/python3.9/site-packages/torch/distributions/distribution.py:216, in Distribution.enumerate_support(self, expand)
    194 def enumerate_support(self, expand=True):
    195     """
    196     Returns tensor containing all values supported by a discrete
    197     distribution. The result will enumerate over dimension 0, so the shape
   (...)
    214         Tensor iterating over dimension 0.
    215     """
--> 216     raise NotImplementedError

NotImplementedError: 
```

However, the attribute `has_enumerate_support` is set to `False` for Normal distribution (again as expected).

```python
normal.has_enumerate_support 
```

```python
False
```

Perhaps, it may be good to look into:

- [ ] Checking if has_enumerate_support is False. If so, directly print, the enumerate_support is defined only for discrete distributions and does not exist for continuous.
- [ ] Or, just changing the message in NotImplementedError to additionally mention this. (though as the error trace shows, this information is there in the doc strings)




### Versions

PyTorch version: 1.10.2
Is debug build: False
CUDA used to build PyTorch: None
ROCM used to build PyTorch: N/A

OS: macOS 12.2 (x86_64)
GCC version: Could not collect
Clang version: 13.0.0 (clang-1300.0.29.30)
CMake version: version 3.21.4
Libc version: N/A

Python version: 3.9.7 | packaged by conda-forge | (default, Sep 29 2021, 20:33:18)  [Clang 11.1.0 ] (64-bit runtime)
Python platform: macOS-12.2-x86_64-i386-64bit
Is CUDA available: False
CUDA runtime version: No CUDA
GPU models and configuration: No CUDA
Nvidia driver version: No CUDA
cuDNN version: No CUDA
HIP runtime version: N/A
MIOpen runtime version: N/A

Versions of relevant libraries:
[pip3] mypy-extensions==0.4.3
[pip3] numpy==1.22.1
[pip3] torch==1.10.2
[pip3] torchaudio==0.10.2
[pip3] torchvision==0.11.3
[conda] blas                      2.113                       mkl    conda-forge
[conda] blas-devel                3.9.0              13_osx64_mkl    conda-forge
[conda] ffmpeg                    4.3                  h0a44026_0    pytorch
[conda] libblas                   3.9.0              13_osx64_mkl    conda-forge
[conda] libcblas                  3.9.0              13_osx64_mkl    conda-forge
[conda] liblapack                 3.9.0              13_osx64_mkl    conda-forge
[conda] liblapacke                3.9.0              13_osx64_mkl    conda-forge
[conda] mkl                       2022.0.0           h89fa619_782    conda-forge
[conda] mkl-devel                 2022.0.0           h694c41f_783    conda-forge
[conda] mkl-include               2022.0.0           hf224eb6_782    conda-forge
[conda] mypy_extensions           0.4.3            py39h6e9494a_4    conda-forge
[conda] numpy                     1.22.1           py39h9d9ce41_0    conda-forge
[conda] pytorch                   1.10.2                  py3.9_0    pytorch
[conda] torch                     1.10.2                   pypi_0    pypi
[conda] torchaudio                0.10.2                 py39_cpu    pytorch
[conda] torchvision               0.11.3                 py39_cpu    pytorch

cc @fritzo @neerajprad @alicanb @nikitaved