pandas requires .5.3 see pandas-dev/pandas/issues/27558

Author: javierluraschi

.travis.yml

@@ -58,14 +58,14 @@ matrix:
       script:
         - R CMD build --no-build-vignettes .
         - Rscript -e 'install.packages(dir(".", pattern = "pins_"))'
-        - pytest python/pins/tests/test.py
+        - python3.6 -m pytest python/pins/tests/test.py
       addons:
         apt:
           update: true
           sources:
             - deadsnakes
           packages:
-            - python3.8
+            - python3.6
             - python3-pip
 os:
   - linux