samba-tool domain: fix an unhandled exception

samba-tool domain: fix an unhandled exception

Uncaught exception on running 'samba-tool domain schemaupgrade'

ERROR(<class 'ModuleNotFoundError'>): uncaught exception - No module named
'markdown' File "/usr/lib64/python3.7/site-packages/samba/netcmd/__init__.py",
line 185, in _run return self.run(*args, **kwargs) File
"/usr/lib64/python3.7/site-packages/samba/netcmd/domain.py", line 4157, in run
from samba.ms_schema_markdown import read_ms_markdown File
"/usr/lib64/python3.7/site-packages/samba/ms_schema_markdown.py", line 26, in
<module> import markdown

Signed-off-by: Amit Kumar amitkuma@redhat.com
Reviewed-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>