pspng no grouperSession error

Erik Coleman [12:33 PM]
More fun with PSP-NG... every so often we are getting this exception when trying to pull subjects to put into a group syncing to AD/LDAP. I can assure you that these users have both a UIN and 'samaccountname' attribute populated, so I don't understand what is causing it to fail. There is the odd message about "no GrouperSession detected" is that a problem?
Stack dump
grouper-daemon;grouper_daemon.log;aws-prod;617683844790;2019-06-19 11:09:36,980: [FullSyncer(uofi_urbana)-Thread] INFO ProgressMonitor.<init>(36) - - Fetching subjects Started: TotalWorkExpected=9
grouper-daemon;grouper_daemon.log;aws-prod;617683844790;2019-06-19 11:09:36,980: [TSUserFetcher-uofi_urbana-full-1] DEBUG LdapProvisioner.fetchTargetSystemUsers(200) - - Fetching 9 users from target system
grouper-daemon;grouper_daemon.log;aws-prod;617683844790;2019-06-19 11:09:36,981: [TSUserFetcher-uofi_urbana-full-1] ERROR Provisioner.evaluateJexlExpression(746) - - Jexl Expression UserSearchFilter 'samAccountName=${edu.internet2.middleware.subject.getAttributeValue('samaccountname')}' could not be evaluated for subject ''650772210'/'person'/'uofinetid'/null' and group 'null/null' which used variableMap '{userSearchBaseDn=dc=ad,dc=uillinois,dc=edu, provisionerType=LdapGroupProvisioner, groupCreationBaseDn=ou=AuthMan,ou=Urbana,dc=ad,dc=uillinois,dc=edu, utils=edu.internet2.middleware.grouper.pspng.PspJexlUtils@320ed7d7, subject='650772210'/'person'/'uofinetid', provisionerName=uofi_urbana, groupSearchBaseDn=ou=AuthMan,ou=Urbana,dc=ad,dc=uillinois,dc=edu}'
java.lang.RuntimeException: Error substituting string: '${edu.internet2.middleware.subject.getAttributeValue('samaccountname')}'
at edu.internet2.middleware.grouper.util.GrouperUtil.substituteExpressionLanguage(GrouperUtil.java:9401)
at edu.internet2.middleware.grouper.pspng.Provisioner.evaluateJexlExpression(Provisioner.java:702)
at edu.internet2.middleware.grouper.pspng.LdapProvisioner.getUserLdapFilter(LdapProvisioner.java:283)
at edu.internet2.middleware.grouper.pspng.LdapProvisioner.fetchTargetSystemUsers(LdapProvisioner.java:211)
at edu.internet2.middleware.grouper.pspng.Provisioner$2.call(Provisioner.java:847)
at edu.internet2.middleware.grouper.pspng.Provisioner$2.call(Provisioner.java:841)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.commons.jexl2.JexlException: edu.internet2.middleware.grouper.util.GrouperUtil.substituteExpressionLanguage@9346![33,68]: 'edu.internet2.middleware.subject.getAttributeValue('samaccountname');' method invocation error
at org.apache.commons.jexl2.Interpreter.call(Interpreter.java:1076)
at org.apache.commons.jexl2.Interpreter.visit(Interpreter.java:1100)
at org.apache.commons.jexl2.parser.ASTMethodNode.jjtAccept(ASTMethodNode.java:18)
at org.apache.commons.jexl2.Interpreter.visit(Interpreter.java:1317)
at org.apache.commons.jexl2.parser.ASTReference.jjtAccept(ASTReference.java:18)
at org.apache.commons.jexl2.Interpreter.interpret(Interpreter.java:232)
at org.apache.commons.jexl2.ExpressionImpl.evaluate(ExpressionImpl.java:65)
at edu.internet2.middleware.grouper.util.GrouperUtil.substituteExpressionLanguage(GrouperUtil.java:9352)
... 9 more
Caused by: java.lang.IllegalStateException: There is no open GrouperSession detected. Make sure to start a grouper session (e.g. GrouperSession.startRootSession() if you want to use a root session ) before calling this method
at edu.internet2.middleware.grouper.GrouperSession.staticGrouperSession(GrouperSession.java:1150)
at edu.internet2.middleware.grouper.GrouperSession.staticGrouperSession(GrouperSession.java:1098)
at edu.internet2.middleware.grouper.subj.SourcesXmlResolver.find(SourcesXmlResolver.java:316)
at edu.internet2.middleware.grouper.subj.CachingResolver.find(CachingResolver.java:143)
at edu.internet2.middleware.grouper.subj.ValidatingResolver.find(ValidatingResolver.java:105)
at edu.internet2.middleware.grouper.SubjectFinder.findByIdAndSource(SubjectFinder.java:504)
at edu.internet2.middleware.grouper.subj.LazySubject.getSubject(LazySubject.java:215)
at edu.internet2.middleware.grouper.subj.LazySubject.getAttributeValue(LazySubject.java:139)
at sun.reflect.GeneratedMethodAccessor985.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.commons.jexl2.internal.MethodExecutor.execute(MethodExecutor.java:64)
at org.apache.commons.jexl2.internal.AbstractExecutor$Method.invoke(AbstractExecutor.java:327)
at org.apache.commons.jexl2.Interpreter.call(Interpreter.java:1068)
... 16 more
grouper-daemon;grouper_daemon.log;aws-prod;617683844790;2019-06-19 11:09:36,981: [TSUserFetcher-uofi_urbana-full-1] WARN Provisioner$2.call(849) - - Batch-fetching subject information failed. Trying fetching information for each subject individually
edu.internet2.middleware.grouper.pspng.PspException: Jexl evaluation failed: Error substituting string: '${edu.internet2.middleware.subject.getAttributeValue('samaccountname')}'
at edu.internet2.middleware.grouper.pspng.Provisioner.evaluateJexlExpression(Provisioner.java:751)
at edu.internet2.middleware.grouper.pspng.LdapProvisioner.getUserLdapFilter(LdapProvisioner.java:283)
at edu.internet2.middleware.grouper.pspng.LdapProvisioner.fetchTargetSystemUsers(LdapProvisioner.java:211)
at edu.internet2.middleware.grouper.pspng.Provisioner$2.call(Provisioner.java:847)
at edu.internet2.middleware.grouper.pspng.Provisioner$2.call(Provisioner.java:841)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)