Fix: Yum module does not use proxy when username is not set #51548 (#51994)

* add test of yum with proxy

* Properly handle unauthenticated yum proxy config

Fixes #51548

* shell executable is bash

lib/ansible/modules/packaging/os/yum.py

@@ -703,7 +703,6 @@ class YumModule(YumDnf):
         # setting system proxy environment and saving old, if exists
         my = self.yum_base()
         namepass = ""
-        proxy_url = ""
         scheme = ["http", "https"]
         old_proxy_env = [os.getenv("http_proxy"), os.getenv("https_proxy")]
         try:
@@ -726,10 +725,7 @@ class YumModule(YumDnf):
                         )
                 else:
                     for item in scheme:
-                        os.environ[item + "_proxy"] = re.sub(
-                            r"(http://)",
-                            r"\g<1>", proxy_url
-                        )
+                        os.environ[item + "_proxy"] = my.conf.proxy
             yield
         except yum.Errors.YumBaseError:
             raise