CopyFile2 not supported in Windows 7

A user reported on discord that dvc add was throwing the following error:

ERROR: unexpected error - function 'CopyFile2' not found

Here's the output of dvc version:

DVC version: 0.82.6
Python version: 3.6.3
Platform: Windows-7-6.1.7601-SP1
Binary: False
Package: pip
Cache: reflink - not supported, hardlink - supported, symlink - not supported

We are using CopyFile2 on Windows to increase the performance of copy (see speedcopy), but that system call was introduced in Windows 8.

The solution was to pip uninstall speedcopy and let DVC fallback to Python's copy implementation.

What should we do?

• Catch AttributeError: function 'CopyFile2' not found and output an actionable error message to fix it.
• State in README / docs that we don't support < Windows 8?
• Nothing?

[shcheklein]

Looks like Windows 7 EOL is already here? Considering that the whole Windows users share for DVC is about 2% or something not sure we should spend too much time on it?

We definitely should introduce some user-friendly message though and change docs is needed.

@shcheklein , totally, looks like it already happened:

EOL: Windows 7, service pack 1*, (mainstream) January 13, 2015 - (extended) January 14, 2020