fix: resolve StopIteration error in BigQuery emulator fixture

Fixes a RuntimeError caused by StopIteration being raised inside a
generator function when Docker container ports cannot be found.

Changes:
- Move container.reload() to the start of retry loop to ensure fresh
  port bindings are available
- Replace unsafe next() call with explicit dict.get() for exact-key
  port matching (e.g., "9050/tcp" instead of startswith pattern)
- Add descriptive error message showing available ports when lookup fails
- Use RuntimeError instead of allowing StopIteration to propagate

This fix ensures all database services (including BigQuery emulator)
can properly start their Docker containers and expose ports reliably.

Resolves issue where BigQuery tests failed with:
"RuntimeError: generator raised StopIteration"

Author: cofin

src/pytest_databases/_service.py

@@ -10,10 +10,10 @@
 
 import filelock
 import pytest
-from docker import DockerClient
 from docker.errors import APIError, ImageNotFound
 from typing_extensions import Self
 
+from docker import DockerClient
 from pytest_databases.helpers import get_xdist_worker_id
 from pytest_databases.types import ServiceContainer
 
@@ -176,17 +176,24 @@ def run(
                 # spins it up and the metadata becomes available, so we're redoing the
                 # check with a small incremental backup here
                 for i in range(10):
+                    container.reload()
                     if any(v for v in container.ports.values()):
                         break
-                    container.reload()
                     time.sleep(0.1 + (i / 10))
                 else:
                     msg = f"Service {name!r} failed to create container"
                     raise ValueError(msg)
 
-        host_port = int(
-            container.ports[next(k for k in container.ports if k.startswith(str(container_port)))][0]["HostPort"]
-        )
+        # Try TCP first (most common), fallback to UDP
+        binding = container.ports.get(f"{container_port}/tcp") or container.ports.get(f"{container_port}/udp")
+        if not binding:
+            msg = (
+                f"Container port {container_port} not found in exposed ports. "
+                f"Available ports: {list(container.ports.keys())}"
+            )
+            raise RuntimeError(msg)
+
+        host_port = int(binding[0]["HostPort"])
         service = ServiceContainer(
             host=container_host,
             port=host_port,

tests/test_redis.py

@@ -95,8 +95,8 @@ def test_two({redis_compatible_service}: RedisService) -> None:
     assert not client.get("one")
     client.set("one", "1")
     assert client.get("one") == b"1"
-    
-    
+
+
 def test_use_same_db({redis_compatible_service}: RedisService) -> None:
     client_0 = redis.Redis(host={redis_compatible_service}.host, port={redis_compatible_service}.port, db=0)
     client_1 = redis.Redis(host={redis_compatible_service}.host, port={redis_compatible_service}.port, db=1)