Oscfs

=====

- fix minor error in urlopen wrapper occuring in some Python versions,
causing an exception upon start.

=====

- fix error if a package filename contained the '' character.
- fix authentication error detection during startup.
- enable urlopenwrapper hack again which speeds up consecutive requests
drastically.
- source code ported to Python3 only, removed all Python2 compatibility.
Source code is now conforming largely to PIP and flake8 standards.

=====

- fix error when reading from some "buildlog" nodes that contained non-utf8
encoding data.
- fix problem with grep on larger files, because more data was returned by
read() than actually requested when unicode data was involved.

=====

- fix read() with offset especially with large files. This fixes use of
various tools when applied on oscfs files e.g. `rpm2cpio` or
`tail *.spec` previously failed or behaved strangely.
- be robust against non-ASCII characters in OBS buildlogs.
- apply caching also to actual file content to be more efficient when e.g.
operating on larger files.

=====

- Added support for running in Python3 with the Python3 osc module installed.
- support mounting of oscfs in non-empty directories.
- minor bugfixes with accessing package and project meta data via `.oscfs`.

=====

- Fixed a bug with accessing the artifacts in the ``.oscfs/binaries/``
per-package sub-directory. The data was very inefficiently retrieved
from the OBS server resulting in extremely low read performance.