Fix RTD error

Co-authored-by: Basile Pinsard  <[email protected]>

Author: me-pic

.readthedocs.yml

@@ -8,7 +8,7 @@ version: 2
 build:
   os: "ubuntu-20.04"
   tools:
-    python: "3.7"
+    python: "3.9"
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:
@@ -20,3 +20,4 @@ python:
       path: .
       extra_requirements:
         - doc
+        - reports