I have been trying to build r56184 (I think this is the 17.3 release) and it was failing with:

/Users/wholtz/code/labkey/trunk/server/modules/query/src/org/labkey/query/controllers/AbstractExternalSchemaForm.java:18: error: package org.apache.commons.lang does not exist
import org.apache.commons.lang.StringUtils;
                              ^
/Users/wholtz/code/labkey/trunk/server/modules/query/src/org/labkey/query/controllers/AbstractExternalSchemaForm.java:49: error: cannot find symbol
        if (StringUtils.isBlank(bean.getUserSchemaName()))
            ^
  symbol:   variable StringUtils ```

It appears that org.apache.commons:commons-lang changed to org.apache.commons:commons-lang3 and that the dependency on org.apache.commons:commons-lang is no longer declared. 
``` ./gradlew :server:modules:core:dependencies | grep lang ``` only gives command-lang3:3.5 results. I'm pretty clueless about setting up dependencies in gradle, but I edited server/modules/query/build.gradle to include ``` compile group: 'commons-lang', name: 'commons-lang', version: '2.6' ``` within the dependencies block and was then able to get the build to successfully complete. There may be better ways to do this.

I solved my problem but wanted to post here in case someone else hits this or if an improvement needs to be made to the dependencies definitions.

-Will