Replace assert in reverse_jordan_wigner.py

src/openfermion/transforms/opconversions/reverse_jordan_wigner.py

@@ -81,7 +81,8 @@ def reverse_jordan_wigner(qubit_operator, n_qubits=None):
                     working_term.terms[list(working_term.terms)[0]] = 1.0
 
                 # Get next non-identity operator acting below 'working_qubit'.
-                assert len(working_term.terms) == 1
+                if len(working_term.terms) != 1:
+                    raise ValueError('Qubit operator term needs to be a single term')
                 working_qubit = pauli_operator[0] - 1
                 for working_operator in reversed(list(working_term.terms)[0]):
                     if working_operator[0] <= working_qubit: