Add an __init__.py in repo root to prevent import confusion

Author: maresb

__init__.py

@@ -0,0 +1,11 @@
+from pathlib import Path
+
+
+repo_root = Path(__file__).parent
+
+raise RuntimeError(
+    f"Python is looking for PyTensor in {repo_root}, but it's "
+    f"actually located in {repo_root / 'pytensor'}. Probably "
+    f"you need to change your working directory from {Path.cwd()} "
+    f"to {repo_root}."
+)