Pandas/Cython doesn't currently support 3.7. Once it does we need to enable 3.7 testing on Monitoring.

Collecting pandas>=0.17.1 (from google-cloud-monitoring==0.29.0)
Using cached https://files.pythonhosted.org/packages/08/01/803834bc8a4e708aedebb133095a88a4dad9f45bbaf5ad777d2bea543c7e/pandas-0.22.0.tar.gz
Could not find a version that satisfies the requirement Cython (from versions: )
No matching distribution found for Cython