Why am I getting CategoryNotInSchemeError?

CategoryNotInSchemeError is raised when scholia finds a non-empty category label in students.csv that has no matching entry in the corresponding question in scheme.yaml. In other words, a student has been assigned a category that the scheme does not recognise.

What the error tells you. The exception message includes the student identifier, the question name, the unrecognised category label, and the list of valid labels that are defined for that question. For example:

CategoryNotInSchemeError: Student 's007' has category 'd' for question
'q1(a)', which is not defined in the scheme. Valid categories are:
['a', 'b', 'c'].

Common causes.

• A typo in students.csv. Category labels are case-sensitive, so B and b are different. Check that the label in the CSV matches the label in scheme.yaml exactly.
• A category was renamed or removed from scheme.yaml after some students had already been assigned to it. Re-run scholia update to sync the headers, then correct the affected cells.
• A new category was added to students.csv before it was added to scheme.yaml. Add the category to the scheme first, or leave the cell blank until the scheme is ready.

How to fix it. Open students.csv and find the row for the student named in the error. Locate the column for the question named in the error. Either correct the label to one of the valid categories listed in the error message, or clear the cell to leave the question unassigned (an empty cell is treated as not yet marked and does not raise an error).

Why scholia raises an error rather than ignoring the label. An unrecognised category is almost always a mistake. Silently treating it as "not yet marked" would hide the problem: the student would appear incomplete in the summary and receive no marks for that question, with no indication that something was wrong. Raising an error immediately makes the problem visible and prevents incorrect marks and feedback from being generated.