Fix the pandas version to 0.23 for testing

containers/Dockerfile-test-suite-python27

@@ -20,7 +20,7 @@ echo ". /opt/conda/etc/profile.d/conda.sh" >> ~/.bashrc && \
 echo "conda activate base" >> ~/.bashrc
 
 # Install conda-installable programs
-RUN conda install -y numpy scipy matplotlib pandas
+RUN conda install -y numpy scipy matplotlib pandas==0.23
 
 RUN conda install -c conda-forge deepdish
 

containers/Dockerfile-test-suite-python37

@@ -21,7 +21,7 @@ echo ". /opt/conda/etc/profile.d/conda.sh" >> ~/.bashrc && \
 echo "conda activate base" >> ~/.bashrc
 
 # Install conda-installable programs
-RUN conda install -y numpy scipy matplotlib pandas
+RUN conda install -y numpy scipy matplotlib pandas==0.23
 
 RUN conda install -c conda-forge deepdish