Is your feature request related to a problem? Please describe.
There has been a few Issues and discussions regarding readEnvironmentVariable() and how to troubleshoot when it doesn't work as expected.

To make troubleshooting the use of readEnvironmentVariable() easier, it would be helpful if the method also (trace)logged the name of all environment variables found.

Describe the solution you'd like
Write name of any environment variable found to the trace log.

The details around when to log might need some discussion, my thoughts are one of:

• Each time readEnvironmentVariable() is called
• Once per compilation where readEnvironmentVariable() will be called
• Only if readEnvironmentVariable() fails to find a value

Since environment variables might contain sensitive information, I do not think their values should be logged, but getting a list of all the names would make it a lot easier to determine that the expected variable actually exists in the right scope.