log4j:ERROR Could not find value for key log4j.appender.Appender2

```
log4j:ERROR Could not find value for key log4j.appender.Appender2
log4j:ERROR Could not instantiate appender named "Appender2".
```

is caused by:
https://github.com/in28minutes/SpringMvcStepByStep/blob/master/Step14.md

`log4j.rootLogger=TRACE, Appender1, Appender2`

Appender2 is not defined.