CIMATE-917 Bocumentation build error with Python3
diff --git a/docs/source/conf.py b/docs/source/conf.py
index b0b511c..5e101e9 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -14,6 +14,8 @@
 import sys
 import os
 
+autodoc_mock_imports = ["esgf"]
+
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.