improve error message of quantumcircuit (#6132)
improve error message of quantumcircuit (#6132)

* improve error message of quantumcircuit

* fix linting

Co-authored-by: Pieter Eendebak <02a33c200f78738583c0f748e10aa00146a7c643@gmail.com>
Co-authored-by: mergify[bot] <b09a6ee808b67e98a221404e7aaa52e0398a4954@users.noreply.github.com>
QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py