chore: block network access from unit tests (#2732)

# What does this PR do?
this blocks network access for all `tests/unit/` tests.
`tests/integration/` are untouched.

it also introduces an `allow_network` marker to explicitly allow network
access.

## Test Plan
`./scripts/unit-tests.sh`

tests/unit/conftest.py

@@ -4,6 +4,17 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
+import pytest_socket
+
 # We need to import the fixtures here so that pytest can find them
 # but ruff doesn't think they are used and removes the import. "noqa: F401" prevents them from being removed
 from .fixtures import cached_disk_dist_registry, disk_dist_registry, sqlite_kvstore  # noqa: F401
+
+
+def pytest_runtest_setup(item):
+    """Setup for each test - check if network access should be allowed."""
+    if "allow_network" in item.keywords:
+        pytest_socket.enable_socket()
+    else:
+        # Allowing Unix sockets is necessary for some tests that use local servers and mocks
+        pytest_socket.disable_socket(allow_unix_socket=True)

tests/unit/providers/inference/test_remote_vllm.py

@@ -393,6 +393,7 @@ async def test_process_vllm_chat_completion_stream_response_no_choices():
     assert chunks[0].event.event_type.value == "start"
 
 
+@pytest.mark.allow_network
 def test_chat_completion_doesnt_block_event_loop(caplog):
     loop = asyncio.new_event_loop()
     loop.set_debug(True)

tests/unit/rag/test_vector_store.py

@@ -123,6 +123,7 @@ class TestVectorStore:
         content = await content_from_doc(doc)
         assert content in DUMMY_PDF_TEXT_CHOICES
 
+    @pytest.mark.allow_network
     async def test_downloads_pdf_and_returns_content(self):
         # Using GitHub to host the PDF file
         url = "https://raw.githubusercontent.com/meta-llama/llama-stack/da035d69cfca915318eaf485770a467ca3c2a238/llama_stack/providers/tests/memory/fixtures/dummy.pdf"
@@ -135,6 +136,7 @@ class TestVectorStore:
         content = await content_from_doc(doc)
         assert content in DUMMY_PDF_TEXT_CHOICES
 
+    @pytest.mark.allow_network
     async def test_downloads_pdf_and_returns_content_with_url_object(self):
         # Using GitHub to host the PDF file
         url = "https://raw.githubusercontent.com/meta-llama/llama-stack/da035d69cfca915318eaf485770a467ca3c2a238/llama_stack/providers/tests/memory/fixtures/dummy.pdf"