It seems that older versions of SQLAlchemy and SQLAlchemy-Utils depended on six, so there was no need to declare it here.
However, latest releases of SQLAlchemy and SQLAlchemy-Utils no longer depend on six, but SQLAlchemy-Continuum does in fact import six, so we need to declare it as a dependency.
It seems that older versions of SQLAlchemy and SQLAlchemy-Utils depended on six, so there was no need to declare it here.
However, latest releases of SQLAlchemy and SQLAlchemy-Utils no longer depend on six, but SQLAlchemy-Continuum does in fact import six, so we need to declare it as a dependency.