API: Fix semaphore handling and chat completion errors

Chat completions previously always yielded a final packet to say that
a generation finished. However, this caused errors that a yield was
executed after GeneratorExit. This is correctly stated because python's
garbage collector can't clean up the generator after exiting due to the
finally block executing.

In addition, SSE endpoints close off the connection, so the finish packet
can only be yielded when the response has completed, so ignore yield on
exception.

Signed-off-by: kingbri <bdashore3@proton.me>

main.py

@@ -201,8 +201,6 @@ async def generate_completion(request: Request, data: CompletionRequest):
                                                           model_path.name)
 
                     yield get_sse_packet(response.json(ensure_ascii=False))
-            except GeneratorExit:
-                print("Completion response aborted")
             except Exception as e:
                 yield get_generator_error(e)
 
@@ -233,6 +231,7 @@ async def generate_chat_completion(request: Request, data: ChatCompletionRequest
         const_id = f"chatcmpl-{uuid4().hex}"
         async def generator():
             try:
+                raise ValueError("Error!")
                 new_generation = model_container.generate_gen(prompt, **data.to_gen_params())
                 for (part, _, _) in new_generation:
                     if await request.is_disconnected():
@@ -244,20 +243,17 @@ async def generate_chat_completion(request: Request, data: ChatCompletionRequest
                         model_path.name
                     )
 
-                    yield get_sse_packet(response.json(ensure_ascii=False))                        
-            except GeneratorExit:
-                print("Chat completion response aborted")
-            except Exception as e:
-                yield get_generator_error(e)
-            finally:
-                # Always finish no matter what
-                # FIXME: An error currently fires here since the generator is closed, move this somewhere else
+                    yield get_sse_packet(response.json(ensure_ascii=False))
+
+                # Yield a finish response on successful generation
                 finish_response = create_chat_completion_stream_chunk(
                     const_id,
                     finish_reason = "stop"
                 )
 
                 yield get_sse_packet(finish_response.json(ensure_ascii=False))
+            except Exception as e:
+                yield get_generator_error(e)
 
         return StreamingResponse(
             generate_with_semaphore(generator),