bug fix "referenced before assignment"

[aaita92]

Summary

at the line 865 rise the error:

" UnboundLocalError: local variable 'qc' referenced before assignment"

when "state_in" and "quantum_registers" are provided.
This is due to the fact that when the if at line 863 is satisfied and the error at line 865 doesn't arise no "qc" variable is declared, generating the error.

Details and comments

[claassistantio]

All committers have signed the CLA.

[woodsp-ibm]

Thanks for reporting and providing a fix for the issue. Currently the build is failing the lint check on the updated code. If you click Details for the Travis CI where it has the red X then you will see a list of Jobs. One of which has a red X against it. Clicking that will show the build log. I copied the relevant lines here that given the failure reason for convenience:

qiskit/aqua/operators/weighted_pauli_operator.py:861:1: W293 blank line contains whitespace
qiskit/aqua/operators/weighted_pauli_operator.py:863:9: E303 too many blank lines (2)
qiskit/aqua/operators/weighted_pauli_operator.py:865:95: W291 trailing whitespace
qiskit/aqua/operators/weighted_pauli_operator.py:866:45: W291 trailing whitespace

If you have pylint installed locally you can run make lint locally to run the same check.

[woodsp-ibm]

Thanks again for taking the time and providing this fix!