There appears to be a problem with the PO file
Where the comment is duplicated and one of it (top line) doesn't have a linenumber reference at the end:
msgstr "Trình Đơn -- Menu"
This is causing sphinx to abort with error upon write (dump_po) in the file
File ".local/lib/python3.6/site-packages/babel/messages/pofile.py", line 592, in write_po for filename, lineno in sorted(message.locations):
TypeError: '<' not supported between instances of 'int' and 'NoneType'
The problem is caused by the line
since it was expecting to see that there is a line number (int) and not 'None', due to the missing number. This is happening with every language sets.