Theme doesn't render

I get this error when I try to render the my theme. What should I do?

Error loading template lms/static/css/bootstrap/lms-main-rtl.css
Traceback (most recent call last):
  File "main.py", line 23, in <module>
  File "tutor/commands/cli.py", line 30, in main
  File "click/core.py", line 1137, in __call__
  File "click/core.py", line 1062, in main
  File "click/core.py", line 1668, in invoke
  File "click/core.py", line 1668, in invoke
  File "click/core.py", line 1404, in invoke
  File "click/core.py", line 763, in invoke
  File "click/decorators.py", line 38, in new_func
  File "tutor/commands/config.py", line 86, in render
  File "tutor/env.py", line 186, in render_all_to
  File "tutor/env.py", line 167, in render_template
  File "jinja2/environment.py", line 997, in get_template
  File "jinja2/environment.py", line 958, in _load_template
  File "jinja2/loaders.py", line 137, in load
  File "jinja2/environment.py", line 757, in compile
  File "jinja2/environment.py", line 925, in handle_exception
  File "<unknown>", line 6, in template
jinja2.exceptions.TemplateSyntaxError: Missing end of comment tag
[69471] Failed to execute script main
make: *** [Makefile:2: render] Error 1

Hi @nahroege! What’s at line 6 of the file lms-main-rtl.css in your custom theme? It looks there is a syntax error right there.