See https://travis-ci.org/pygeos/pygeos/jobs/652638801

The master build worked. I took a diff between the dependencies in the master build and the dependencies in the link and there was only one:

pycparser-2.19             |             py_2          88 KB  conda-forge

Instead of

pycparser-2.19             |           py37_1         171 KB  conda-forge

Which seems completely unrelated, although I don't know how pycparser is used in our test suite.