port uncompress/tar_file.py to python3

[dimpase]

the internals of python's tarfile.py have changed, and the override of _extract_member in uncompress/tar_file.py misses parameters. Namely, if your system python is python3, you will get

Setting up build directory for patch-2.7.5
Traceback (most recent call last):
  File "/mnt/opt/Sage/sage-clang/build/bin/sage-uncompress-spkg", line 23, in <module>
    run()
  File "/mnt/opt/Sage/sage-clang/build/bin/../sage_bootstrap/uncompress/cmdline.py", line 72, in run
    unpack_archive(archive, dirname)
  File "/mnt/opt/Sage/sage-clang/build/bin/../sage_bootstrap/uncompress/action.py", line 68, in unpack_archive
    archive.extractall(members=archive.names)
  File "/mnt/opt/Sage/sage-clang/build/bin/../sage_bootstrap/uncompress/tar_file.py", line 90, in extractall
    members=members)
  File "/usr/lib64/python3.5/tarfile.py", line 1998, in extractall
    numeric_owner=numeric_owner)
  File "/usr/lib64/python3.5/tarfile.py", line 2040, in extract
    numeric_owner=numeric_owner)
TypeError: _extract_member() got an unexpected keyword argument 'set_attrs'

as soon as you start a clean build of Sage.

[dimpase]

while I am at it:

$ pylint tar_file.py 
No config file found, using default configuration
************* Module sage_bootstrap.uncompress.tar_file
W: 67, 4: Parameters differ from overridden 'chmod' method (arguments-differ)
W: 74, 4: Parameters differ from overridden 'utime' method (arguments-differ)
W: 79, 4: Parameters differ from overridden 'extractall' method (arguments-differ)
W:103, 4: Parameters differ from overridden '_extract_member' method (arguments-differ)
W:153,15: Catching too general exception Exception (broad-except)

------------------------------------------------------------------
Your code has been rated at 9.09/10 (previous run: 9.09/10, +0.00)

[embray]

I don't think I've tried building Sage with Python 3 as the default "bootstrap" Python, but indeed that should definitely work, especially as more distros are finally defaulting to Python 3.

Is this the only issue you've encountered so far?

[dimpase]

This is the first bug one hits, I didn't go further. I suppose that merely adding the extra (Python3-only) key arguments to the functions overriding the ones in the library will do here (as key args are optional, and so more is OK for Python2 as well).

[embray]

From the sound of things this is a regression too, since it used to work on Python 3 but now it doesn't.

[embray]

New commits:

​d6e32e2

Fix compatibility with newer versions of the tarfile module in Python 3

[chapoton]

missing blank lines after .. note:: twice

[gh-embray]

Okay, but that isn't strictly needed by RST I don't think.

[chapoton]

sorry for the bikesheding. I would be happy to give a positive review, but I would prefer if Dima tests if it works.

This seems to have hurt somebody : ​https://groups.google.com/forum/#!topic/sage-support/UmGFtjcnm6Y

[gh-embray]

Yeah, I've already talked to Viviane about it.

[chapoton]

Did she try the branch here ?

[dimpase]

works, and docs build