Fix misleading missing environment variable error message

Author: orlnub123

CHANGELOG.md

@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 
 - Ensured Meta is a class.
 - Fixed `Env.prefixed` not resetting the prefix on exceptions.
+- Fixed misleading missing environment variable error messages.
 
 ## [0.1.2] - 2019-03-17
 

class_settings/env.py

@@ -56,7 +56,7 @@ def __call__(self, name=None, *, prefix=missing, default=missing, optional=False
             return os.environ[name]
         except KeyError:
             raise ImproperlyConfigured(
-                "Environment variable {!r} not set".format(name.upper())
+                "Environment variable {!r} not set".format(name)
             ) from None
 
     def __getattr__(self, name):