Avoid conflict of list comprehension variable
Avoid conflict of list comprehension variable

Under Python 2, the variable 'i' could be altered, and affect the loop
condition so that it would exit at a surprising time.

See https://lgtm.com/projects/g/sympy/sympy/snapshot/dist-1950035-1494665740009/files/sympy/physics/quantum/cg.py#V609

kaushik94/sympy,kaushik94/sympy,kaushik94/sympy