ERROR: Build step failed with exception
java.lang.IllegalArgumentException: Null value not allowed as an environment variable: REPOVERSION
	at hudson.EnvVars.put(EnvVars.java:356)
	at hudson.model.StringParameterValue.buildEnvironment(StringParameterValue.java:56)
	at hudson.model.ParametersAction.buildEnvVars(ParametersAction.java:89)
	at hudson.model.AbstractBuild.getEnvironment(AbstractBuild.java:953)
	at hudson.plugins.gradle.Gradle.performTask(Gradle.java:127)
	at hudson.plugins.gradle.Gradle.perform(Gradle.java:118)
	at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
	at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:785)
	at hudson.model.Build$BuildExecution.build(Build.java:205)
	at hudson.model.Build$BuildExecution.doRun(Build.java:162)
	at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:537)
	at hudson.model.Run.execute(Run.java:1741)
	at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
	at hudson.model.ResourceController.execute(ResourceController.java:98)
	at hudson.model.Executor.run(Executor.java:408)
Build step 'Invoke Gradle script' marked build as failure
ERROR: Failed to evaluate groovy script.
java.lang.IllegalArgumentException: Null value not allowed as an environment variable: REPOVERSION
	at hudson.EnvVars.put(EnvVars.java:356)
	at hudson.model.StringParameterValue.buildEnvironment(StringParameterValue.java:56)
	at hudson.model.ParametersAction.buildEnvVars(ParametersAction.java:89)
	at hudson.model.AbstractBuild.getEnvironment(AbstractBuild.java:953)
	at hudson.model.AbstractBuild$getEnvironment.call(Unknown Source)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
	at notifybuild.run(notifybuild.groovy:12)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:580)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:627)
	at groovy.lang.Script.evaluate(Script.java:219)
	at groovy.lang.Script$evaluate.callCurrent(Unknown Source)
	at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:46)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
	at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
	at Script1.run(Script1.groovy:1)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:580)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:618)
	at groovy.lang.GroovyShell.evaluate(GroovyShell.java:589)
	at org.jvnet.hudson.plugins.groovypostbuild.GroovyPostbuildRecorder.perform(GroovyPostbuildRecorder.java:276)
	at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
	at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:785)
	at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:726)
	at hudson.model.Build$BuildExecution.post2(Build.java:185)
	at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:671)
	at hudson.model.Run.execute(Run.java:1766)
	at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
	at hudson.model.ResourceController.execute(ResourceController.java:98)
	at hudson.model.Executor.run(Executor.java:408)
Build step 'Groovy Postbuild' marked build as failure

Jenkins ver. 1.625.3

ver. 1.14

ver. 1.8

import groovyx.net.http.RESTClient
import static groovyx.net.http.ContentType.*
import hudson.model.*

def repoversion = "X"
def env = build.getEnvironment()
def projectName = build.project.getName()
def commit = env['GIT_COMMIT']
int CONNECTION_TIMEOUT  = 30*1000;
 int SOCKET_TIMEOUT = 45*1000;

try{
 def solnet = new RESTClient( 'http://ip_adress/' )
 solnet.getClient().getParams().setParameter("http.connection.timeout", new Integer(CONNECTION_TIMEOUT))
 solnet.getClient().getParams().setParameter("http.socket.timeout", new Integer(SOCKET_TIMEOUT))

 def resp = solnet.get( path : 'repo_get_version.php', query: ['name':projectName,'revision':commit])
 if(resp.status == 200){
  repoversion = resp.data.version
 }
}
catch(Exception e){
   println e.getMessage()
}

def pa = new ParametersAction([
  new StringParameterValue("REPOVERSION", repoversion)
])

// add variable to current job
Thread.currentThread().executable.addAction(pa)