specify the python package versions to be installed

Author: z5ouyang

config.sh

@@ -109,11 +109,11 @@ pip install boto3==1.14.39
 git clone https://github.com/theislab/scanpy.git
 cd scanpy;git checkout 2ea9f836cec6e12a5cdd37bc4a229d4eadf59d37;cd ..
 pip install scanpy/
-pip install jupyter_client
-pip install jupytext
-pip install nbconvert
+pip install jupyter_client==6.1.7
+pip install jupytext==1.6.0
+pip install nbconvert==5.6.1
 pip install rpy2==3.3.5
-pip install pyarrow
+pip install pyarrow==1.0.1
 
 # old versions
 # pip install git+https://github.com/theislab/scanpy.git@split_show