docs(readme): clarify docintel api-key setup

README.md

@@ -134,12 +134,15 @@ To find available plugins, search GitHub for the hashtag `#markitdown-plugin`. T
 
 ### Azure Document Intelligence
 
-To use Microsoft Document Intelligence for conversion:
+To use Microsoft Document Intelligence for conversion from the command line:
 
 ```bash
+export AZURE_API_KEY="<document_intelligence_api_key>"
 markitdown path-to-file.pdf -o document.md -d -e "<document_intelligence_endpoint>"
 ```
 
+If `AZURE_API_KEY` is not set, MarkItDown will fall back to `DefaultAzureCredential`.
+
 More information about how to set up an Azure Document Intelligence Resource can be found [here](https://learn.microsoft.com/en-us/azure/ai-services/document-intelligence/how-to-guides/create-document-intelligence-resource?view=doc-intel-4.0.0)
 
 ### Python API
@@ -154,16 +157,25 @@ result = md.convert("test.xlsx")
 print(result.text_content)
 ```
 
-Document Intelligence conversion in Python:
+Document Intelligence conversion in Python using an API key:
 
 ```python
+import os
+
+from azure.core.credentials import AzureKeyCredential
 from markitdown import MarkItDown
 
-md = MarkItDown(docintel_endpoint="<document_intelligence_endpoint>")
+md = MarkItDown(
+    docintel_endpoint=os.environ["AZURE_DOC_INT_ENDPOINT"],
+    docintel_credential=AzureKeyCredential(os.environ["AZURE_API_KEY"]),
+    docintel_file_types=["pdf"],
+)
 result = md.convert("test.pdf")
 print(result.text_content)
 ```
 
+If you omit `docintel_credential`, MarkItDown will use `AZURE_API_KEY` when it is set and otherwise fall back to `DefaultAzureCredential`.
+
 To use Large Language Models for image descriptions (currently only for pptx and image files), provide `llm_client` and `llm_model`:
 
 ```python

packages/markitdown/src/markitdown/_markitdown.py

@@ -590,6 +590,7 @@ def _convert(
 
                 # Check if the converter will accept the file, and if so, try to convert it
                 _accepts = False
+                res: Optional[DocumentConverterResult] = None
                 try:
                     _accepts = converter.accepts(file_stream, stream_info, **_kwargs)
                 except NotImplementedError:

packages/markitdown/tests/test_module_misc.py

@@ -382,6 +382,29 @@ def test_exceptions() -> None:
     assert type(exc_info.value.attempts[0].converter).__name__ == "PptxConverter"
 
 
+def test_converter_failure_does_not_raise_unboundlocalerror() -> None:
+    class BrokenPdfConverter:
+        def accepts(self, file_stream, stream_info, **kwargs):
+            return stream_info.extension == ".pdf"
+
+        def convert(self, file_stream, stream_info, **kwargs):
+            raise RuntimeError("broken converter")
+
+    markitdown = MarkItDown(enable_builtins=False, enable_plugins=False)
+    markitdown.register_converter(BrokenPdfConverter())
+
+    with pytest.raises(FileConversionException) as exc_info:
+        markitdown._convert(
+            file_stream=io.BytesIO(b"%PDF-broken"),
+            stream_info_guesses=[
+                StreamInfo(extension=".pdf", mimetype="application/pdf")
+            ],
+        )
+
+    assert len(exc_info.value.attempts) == 1
+    assert type(exc_info.value.attempts[0].converter).__name__ == "BrokenPdfConverter"
+
+
 @pytest.mark.skipif(
     skip_exiftool,
     reason="do not run if exiftool is not installed",