Fetch the submodules in readthedocs with ci_fetch_deps.py

.readthedocs.yml

@@ -9,17 +9,15 @@
 version: 2
 
 build:
-  os: ubuntu-20.04
-  tools:
-    python: "3"
-
-submodules:
-    include:
-        - extmod/ulab
-        - frozen
+    os: ubuntu-20.04
+    tools:
+        python: "3"
+    jobs:
+        post_install:
+            - python tools/ci_fetch_deps.py docs HEAD
 
 formats:
-  - pdf
+    - pdf
 
 python:
     install:

tools/ci_fetch_deps.py

@@ -68,7 +68,7 @@ submodules = []
 if target == "test":
     submodules = ["extmod/", "lib/", "tools/", "extmod/ulab", "lib/berkeley-db-1.xx"]
 elif target == "docs":
-    # NOTE: must match .readthedocs.yml as this script is not run by readthedocs
+    # used in .readthedocs.yml to generate RTD
     submodules = ["extmod/ulab/", "frozen/"]
 elif target == "mpy-cross-mac":
     submodules = ["tools/"]  # for huffman