Description of problem:
Importing btrfs from the python3-btrfs package fails immediately upon import with an exception.

Version-Release number of selected component (if applicable):
python3-btrfs-8-5.fc29.noarch

How reproducible:
Every time.

Steps to Reproduce:
Just import it. btrfs-heatmap uses the python3 version, if you want an example of something in the distribution that fails as a result of this.

Actual results:
$ python3
Python 3.7.0 (default, Aug 30 2018, 14:32:33)
[GCC 8.2.1 20180801 (Red Hat 8.2.1-2)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import btrfs
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.7/site-packages/btrfs/__init__.py", line 23, in <module>
    from btrfs.ctree import FileSystem  # noqa
  File "/usr/lib/python3.7/site-packages/btrfs/ctree.py", line 352, in <module>
    import btrfs.ioctl  # noqa
  File "/usr/lib/python3.7/site-packages/btrfs/ioctl.py", line 215, in <module>
    ioctl_search_key.format.decode(), 4096 - ioctl_search_key.size))
AttributeError: 'str' object has no attribute 'decode'

Expected results:
No errors.