Fix the everest doc generator

src/everest/docs/__main__.py

@@ -1,15 +1,25 @@
+import sys
 from pathlib import Path
 
 from everest.docs.generate_docs_from_config_spec import generate_docs_pydantic_to_rst
 
-committed_file = (
-    Path(__file__).parents[3] / "docs" / "everest" / "config_generated.rst"
-).resolve()
+GENERATED_FILE = Path("docs") / "everest" / "config_generated.rst"
 
+parts = GENERATED_FILE.parts
+while parts and not Path(*parts).exists():
+    parts = parts[1:]
+if not parts:
+    print(
+        f"""The file to update ('{GENERATED_FILE}') was not found.
+The generator must be run from one of the parent directories of
+'{GENERATED_FILE.parts[-1]}' within the ERT source directory.
+Please change the current directory accordingly and re-run."""
+    )
+    sys.exit()
 
-print(f"Writing new docs contents to {committed_file}")
 docs_content = generate_docs_pydantic_to_rst()
-with open(committed_file, "w", encoding="utf-8") as fp:
+with Path(*parts).open("w", encoding="utf-8") as fp:
     fp.write(docs_content)
 
-print(f"Writing updated docs to {committed_file} complete, you may now commit it.")
+print(f"Generated docs written to {GENERATED_FILE}")
+print("Please commit the generated file.")