Remove unused module + enhance code patterns

[alaabenfatma]

This PR targets this issue: #848

What's new:

• Import modules with respect to alphabetical order
• Remove unused module MetaflowException
• Elegantly check the Python version to know what modules to import
  • Use a more explicit LBYL instead of EAPF

[savingoyal]

@alaabenfatma Thanks for the PR! The codebase currently doesn't advocate for either of EAPF or LBYL, so I am not sure if modifying the version check would achieve any goal.
Removing the unused module is a very welcome change. If you can decouple it from the LBYL change, we can get this PR merged.

[alaabenfatma]

@alaabenfatma Thanks for the PR! The codebase currently doesn't advocate for either of EAPF or LBYL, so I am not sure if modifying the version check would achieve any goal. Removing the unused module is a very welcome change. If you can decouple it from the LBYL change, we can get this PR merged.

@savingoyal Thanks for the review. I decoupled the LBYL part from the PR as requested.
I suggested the use of LBYL in order to make the code more consistent with the rest of the codebase.
The rest of the codebase uses LYBL instead of EAPF:
Examples:

• metaflow/metaflow/mflog/tee.py

  Line 13 in 5297918

  if sys.version_info < (3, 0):

• metaflow/metaflow/mflog/redirect_streams.py

  Line 16 in 5297918

  if sys.version_info < (3, 0):

[savingoyal]

@alaabenfatma Thanks for the PR! The codebase currently doesn't advocate for either of EAPF or LBYL, so I am not sure if modifying the version check would achieve any goal. Removing the unused module is a very welcome change. If you can decouple it from the LBYL change, we can get this PR merged.

@savingoyal Thanks for the review. I decoupled the LBYL part from the PR as requested. I suggested the use of LBYL in order to make the code more consistent with the rest of the codebase. The rest of the codebase uses LYBL instead of EAPF: Examples:

• metaflow/metaflow/mflog/tee.py

  Line 13 in 5297918

  if sys.version_info < (3, 0):

• metaflow/metaflow/mflog/redirect_streams.py

  Line 16 in 5297918

  if sys.version_info < (3, 0):

Thanks for the edit! Re: EAPF vs LBYL - unfortunately there isn't any consistency in the code base today - EAPF example - https://github.com/Netflix/metaflow/blob/master/metaflow/util.py#L14