Test on GitHub with httpbin from a container

Avoid failures due to the web service.

.github/workflows/build.yml

@@ -30,6 +30,12 @@ jobs:
           - python-version: "3.8"
             toxenv: minreqs
 
+    services:
+      httpbin:
+        image: kennethreitz/httpbin
+        ports:
+          - 8080:80
+
     steps:
       - name: Install OS dependencies
         run: |

tests/checker/test_httpbin.py

@@ -16,15 +16,19 @@
 """
 Test http stuff with httpbin.org.
 """
+import os
 import re
 from tests import need_network
 from . import LinkCheckTest
 
 
 def get_httpbin_url(path):
-    """Get httpbin URL. Note that this also could be a local
-    httpbin installation, but right now this uses the official site."""
-    return "http://httpbin.org%s" % path
+    """Get httpbin URL."""
+    if "CI" in os.environ:
+        host = "localhost:8080"
+    else:
+        host = "httpbin.org"
+    return f"http://{host}{path}"
 
 
 class TestHttpbin(LinkCheckTest):