Installing pandas 0.20.3 on Google Cloud Dataflow takes a very long time

When using the Apache Beam Python SDK 2.0.0 on Google Cloud Dataflow, it takes forever (about 8 minutes) to install Pandas 0.20.3. The install mainly hangs on the message Running setup.py bdist_wheel for pandas: still running.... On my machine, however, installing the same version of pandas doesn't even take 30 seconds (even after clearing pip cache). Installing pandas takes about a third of the cost of running my pipeline right now. Any ideas on why this takes so much time?