…py-common (#6933)

Fix a strange bug introduced by #6832 which would only occur in environments with both Python 2 and Python 3 installed (e.g., the PMon container). Error messages such as the following would be seen:

```
ERR pmon#ledd[29]: Failed to load ledutil: module 'importlib' has no attribute 'machinery'
```

This is very odd, and it seems like the Python 2 version of importlib, which is basically just a stub, is taking precedence over the Python 3 version. I found that this occurs when calling `import importlib`. However, calling `import importlib.machinery` and `import importlib.util` causes the proper package to be referenced, and the `machinery` and `util` modules are loaded successfully. This is how it is specified in examples in the official documentation, however there is nothing mentioned regarding that it *should* be done this way or that `import importlib` is unreliable.

Also, since sonic-py-common is still used in environments with Python 2 installed we should maintain support for both Python 2 and 3 until we completely deprecate Python 2, so I have added this back in.

…py-common (sonic-net#6933)

Fix a strange bug introduced by sonic-net#6832 which would only occur in environments with both Python 2 and Python 3 installed (e.g., the PMon container). Error messages such as the following would be seen:

```
ERR pmon#ledd[29]: Failed to load ledutil: module 'importlib' has no attribute 'machinery'
```

This is very odd, and it seems like the Python 2 version of importlib, which is basically just a stub, is taking precedence over the Python 3 version. I found that this occurs when calling `import importlib`. However, calling `import importlib.machinery` and `import importlib.util` causes the proper package to be referenced, and the `machinery` and `util` modules are loaded successfully. This is how it is specified in examples in the official documentation, however there is nothing mentioned regarding that it *should* be done this way or that `import importlib` is unreliable.

Also, since sonic-py-common is still used in environments with Python 2 installed we should maintain support for both Python 2 and 3 until we completely deprecate Python 2, so I have added this back in.

…py-common (sonic-net#6933)

Fix a strange bug introduced by sonic-net#6832 which would only occur in environments with both Python 2 and Python 3 installed (e.g., the PMon container). Error messages such as the following would be seen:

```
ERR pmon#ledd[29]: Failed to load ledutil: module 'importlib' has no attribute 'machinery'
```

This is very odd, and it seems like the Python 2 version of importlib, which is basically just a stub, is taking precedence over the Python 3 version. I found that this occurs when calling `import importlib`. However, calling `import importlib.machinery` and `import importlib.util` causes the proper package to be referenced, and the `machinery` and `util` modules are loaded successfully. This is how it is specified in examples in the official documentation, however there is nothing mentioned regarding that it *should* be done this way or that `import importlib` is unreliable.

Also, since sonic-py-common is still used in environments with Python 2 installed we should maintain support for both Python 2 and 3 until we completely deprecate Python 2, so I have added this back in.