unused import

Use PEP 8 for naming (yes this is inconsistent even in Python stdlib, but that's no excuse for us), so get_script_for_file or just script_for_file.

You may also want to declare parameter type (filename: pathlib.Path) and return type -> str. Since using pathlib is relatively new in Blender's Python code, I would at least do the former.

Replace '%s' with %r. This will use single quotes, unless there is a single quote in the string, then it'll use double quotes. If both single and double quotes are there, it'll also escape the filename properly.

Alternatively, do an assert "'" not in str(movie), 'Filename should not contain a single quote: %r' % movie before the return statement.

Since this'll probably just be in master, you can use the new format string syntax introduced in Python 3.6:

print(f'fps:{strip.fps}'))

Why not simply use return round(fps, 2)?

Using a list instead of a tuple will allow you to do command.extend(...) or command.append(...) without requiring the existing tuple to be copied. Doesn't matter much, though.

You may want to leave the trailing comma in place. It allows for clean diffs (now and in the future).

You'll want to look into alembic_tests.py for that.

PHP-like string formatting, yay! Finally!