Add test that nbs load

azure-pipelines.yml

@@ -39,8 +39,17 @@ jobs:
       versionSpec: '3.6'
       architecture: 'x64'
 
+    # Install nbformat
+  - script: |
+      pip install nbformat
+    displayName: 'Install nbformat'
+    continueOnError: false
+    
     # check that notebooks are stripped out. if they aren't that means the committer doesn't have the correct configuration for the stripout filter.
   - script: |
+      echo "Trying to load all notebooks"
+      tools/read-nbs
+      
       echo "Check we are starting with clean git checkout"
       if [ -n "$(git status -uno -s)" ]; then echo "git status is not clean"; false; fi
 
@@ -51,4 +60,5 @@ jobs:
       git status -s # display the status to see which nbs need cleaning up
       if [ -n "$(git status -uno -s)" ]; then echo -e "!!! Detected unstripped out notebooks\n!!!Remember to run tools/run-after-git-clone"; false; fi
     displayName: 'Detect unstripped out notebook commits'
+    failOnStderr: true
     continueOnError: false

tools/read-nbs

@@ -0,0 +1,17 @@
+#!/usr/bin/env python3
+
+import nbformat, os
+from pathlib import Path
+
+def read_nbs(path):
+    "Check all notebooks in `path` (and subfolders) can be opened"
+    path,nb_files = Path(path),[]
+    for p,d,f in os.walk(path): nb_files += [Path(p)/f_ for f_ in f if f_.endswith('.ipynb')]
+    for nb in nb_files:
+        try: 
+            with open(nb, 'r') as f: _ = nbformat.reads(f.read(), as_version=4)
+        except Exception as e: 
+            print(f"{nb} is corrupted and can't be opened.")
+            raise e
+
+read_nbs('nbs')