see if python 3.9 fixes the copybutton

readthedocs.yml

@@ -9,7 +9,7 @@ build:
   os: ubuntu-20.04
   tools:
     python: "3.9"
-    nodejs: 16
+    nodejs: "16"
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:

setup.py

@@ -36,5 +36,5 @@ setuptools.setup(
     #                   'matplotlib',
     #                   'astropy',
     #                   ],
-    python_requires='>=3.8',
+    python_requires='>=3.9',
 )