I'm not sure why this was necessary for me, and not others. Without it, I get:

```
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project fcrepo-kernel: Compilation failure: Compilation failure:
[ERROR] /home/chris/fcrepo4/fcrepo-kernel/src/main/java/org/fcrepo/kernel/identifiers/HttpPidMinter.java:[19,38] package org.apache.commons.lang does not exist
[ERROR] /home/chris/fcrepo4/fcrepo-kernel/src/main/java/org/fcrepo/kernel/identifiers/HttpPidMinter.java:[19,1] static import only from classes and interfaces
[ERROR] /home/chris/fcrepo4/fcrepo-kernel/src/main/java/org/fcrepo/kernel/identifiers/HttpPidMinter.java:[87,25] cannot find symbol
[ERROR] symbol:   method isBlank(java.lang.String)
[ERROR] location: class org.fcrepo.kernel.identifiers.HttpPidMinter
[ERROR] /home/chris/fcrepo4/fcrepo-kernel/src/main/java/org/fcrepo/kernel/identifiers/HttpPidMinter.java:[110,14] cannot find symbol
[ERROR] symbol:   method isBlank(java.lang.String)
[ERROR] location: class org.fcrepo.kernel.identifiers.HttpPidMinter
[ERROR] /home/chris/fcrepo4/fcrepo-kernel/src/main/java/org/fcrepo/kernel/identifiers/HttpPidMinter.java:[110,36] cannot find symbol
[ERROR] symbol:   method isBlank(java.lang.String)
[ERROR] location: class org.fcrepo.kernel.identifiers.HttpPidMinter
[ERROR] /home/chris/fcrepo4/fcrepo-kernel/src/main/java/org/fcrepo/kernel/identifiers/HttpPidMinter.java:[139,15] cannot find symbol
[ERROR] symbol:   method isBlank(java.lang.String)
[ERROR] location: class org.fcrepo.kernel.identifiers.HttpPidMinter
```