Add test and update documentation

docs/source/settings.rst

@@ -42,6 +42,10 @@ application specific configuration.
    Loading the config from a Python module requires the ``python:``
    prefix.
 
+.. versionchanged:: 19.8
+   Pre-19.4 behavior of loading a config file without a ``python:``
+   prefix is now restored.
+
 Server Socket
 -------------
 

gunicorn/config.py

@@ -523,6 +523,10 @@ class ConfigFile(Setting):
         .. versionchanged:: 19.4
            Loading the config from a Python module requires the ``python:``
            prefix.
+
+        .. versionchanged:: 19.8
+           Pre-19.4 behavior of loading a config file without a ``python:``
+           prefix is now restored.
         """
 
 class Bind(Setting):

tests/test_config.py

@@ -238,6 +238,20 @@ def test_load_config_module():
     assert app.cfg.proc_name == "fooey"
 
 
+@pytest.mark.parametrize("options", [
+    ["-c", cfg_module()],
+    ["-c", cfg_file()],
+])
+def test_load_fallback(options):
+    cmdline = ["prog_name"]
+    cmdline.extend(options)
+    with AltArgs(cmdline):
+        app = NoConfigApp()
+    assert app.cfg.bind == ["unix:/tmp/bar/baz"]
+    assert app.cfg.workers == 3
+    assert app.cfg.proc_name == "fooey"
+
+
 def test_cli_overrides_config():
     with AltArgs(["prog_name", "-c", cfg_file(), "-b", "blarney"]):
         app = NoConfigApp()