Model.write() behaves differently with .lp and .mps formats

[ryanjoneil]

Describe the bug

If I write the same model to two different files:

m.write('foo.lp')
m.write('foo.mps')

I get two files with different characteristics:

• foo.lp is a text file in LP format.
• foo.mps.mps.gz is a gzipped MPS file with a repeated .mps extension.

Expected behavior

In the example above, I expect to get two files:

• foo.lp - text file in LP format
• foo.mps - text file in MPS format

I do not expect the .mps.mps repeated extension.

I only expect the output to be gzipped if I explicitly add a .gz extension the filename.

Desktop (please complete the following information):

• Operating System, version: macOS 11.6.7
• Python version: 3.7.8
• Python-MIP version (we recommend you to test with the latest version): 1.13.0

[rschwarz]

I think the model.write method simply delegates the call to the underlying solver (CBC or Gurobi), so the offending behavior is likely defined there.

[sebheger]

@ryanjoneil Thanks for reporting this. But, I will close this as it is a duplicate of #164

[ryanjoneil]

I have some follow-up questions, but I will put those on #164.