According to the pep8 tool documentation (https://pep8.readthedocs.org/en/latest/intro.html#error-codes), the reported warnings always are errors (E) or warnings (W).
The Pep8Parser maps this categories to the HIGH priority.

IMO, pep8 warnings are less important than other warnings like pylint and should not use the HIGH priority but LOW for warnings (W) and NORMAL for errors (E).

Is this change acceptable ?

Regards.