Adopt pyzfs from ClusterHQ

This commit introduces several changes:

 * Update LICENSE and project information

 * Give a good PEP8 talk to existing Python source code

 * Add RPM/DEB packaging for pyzfs

 * Fix some outstanding issues with the existing pyzfs code caused by
   changes in the ABI since the last time the code was updated

 * Integrate pyzfs Python unittest with the ZFS Test Suite

 * Add missing libzfs_core functions: lzc_change_key,
   lzc_channel_program, lzc_channel_program_nosync, lzc_load_key,
   lzc_receive_one, lzc_receive_resumable, lzc_receive_with_cmdprops,
   lzc_receive_with_header, lzc_reopen, lzc_send_resume, lzc_sync,
   lzc_unload_key, lzc_remap

Note: this commit slightly changes zfs_ioc_unload_key() ABI. This allow
to differentiate the case where we tried to unload a key on a
non-existing dataset (ENOENT) from the situation where a dataset has
no key loaded: this is consistent with the "change" case where trying
to zfs_ioc_change_key() from a dataset with no key results in EACCES.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #7230

rpm/generic/zfs.spec.in

@@ -216,6 +216,26 @@ Requires:       dracut
 This package contains a dracut module used to construct an initramfs
 image which is ZFS aware.
 
+%if 0%{?_pyzfs}
+%package -n pyzfs
+Summary:        Python wrapper for libzfs_core
+Group:          Development/Languages/Python
+License:        Apache-2.0
+BuildArch:      noarch
+Requires:       libzfs2 = %{version}
+Requires:       libnvpair1 = %{version}
+Requires:       libffi
+Requires:       python >= 2.7
+Requires:       python-cffi
+%if 0%{?rhel}%{?fedora}%{?suse_version}
+BuildRequires:  python-devel
+BuildRequires:  libffi-devel
+%endif
+
+%description -n pyzfs
+This package provides a python wrapper for the libzfs_core C library.
+%endif
+
 %if 0%{?_initramfs}
 %package initramfs
 Summary:        Initramfs module
@@ -383,6 +403,15 @@ systemctl --system daemon-reload >/dev/null || true
 %doc contrib/dracut/README.dracut.markdown
 %{_dracutdir}/modules.d/*
 
+%if 0%{?_pyzfs}
+%files -n pyzfs
+%doc contrib/pyzfs/README
+%doc contrib/pyzfs/LICENSE
+%defattr(-,root,root,-)
+%{python_sitelib}/libzfs_core/*
+%{python_sitelib}/pyzfs*
+%endif
+
 %if 0%{?_initramfs}
 %files initramfs
 %doc contrib/initramfs/README.initramfs.markdown