minor #37538 Add the name of the env to RuntimeException (Simon Frost)

This PR was squashed before being merged into the 5.2-dev branch.

Discussion
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Add the name of the env to RuntimeException

| Q             | A
| ------------- | ---
| Branch?       | master for features
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets |  
| License | MIT
| Doc PR

if you have the name of the env in the exception message it is much easier to find the error

from -> #20

Commits
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00ab757cbb Add the name of the env to RuntimeException

Author: fabpot

EnvVarProcessor.php

@@ -290,6 +290,6 @@ public function getEnv(string $prefix, string $name, \Closure $getEnv)
             return trim($env);
         }
 
-        throw new RuntimeException(sprintf('Unsupported env var prefix "%s".', $prefix));
+        throw new RuntimeException(sprintf('Unsupported env var prefix "%s" for env name "%s".', $prefix, $name));
     }
 }