snowflake + cffi = more sadness

[beckjake]

Describe the bug

We can't build homebrew packages, because the tool we use chokes on version conflicts (reasonable!) and snowflake requires cffi<1.14, but other dependencies fire first and install cffi==1.14.

Steps To Reproduce

pip install dbt==0.16.0rc1 homebrew-pypi-poet
poet --resources dbt

Get an error about version conflicts and cffi.

Expected behavior

I should get some homebrew package stanzas out, not an error.

System information

Which database are you using dbt with?
Any

The output of dbt --version:
N/A

The operating system you're using:
macos

The output of python --version:
Python 3.8.0

Additional context

In what's becoming a real tradition, we need to pin yet another snowflake dependency in the root package, in this case cffi<1.14.

[beckjake]

fixed in #2181