Coq currently has Jenkins 1.640 installed on its production server.  I am attempting to upgrade this to Jenkins 2.222.4 LTS via the web management interface at https://ci.inria.fr/project/coq/cisoftware.  I have installed Jenkins 2.222.4 LTS on the Qualification sever via the web interface, and then I clicked the "Setup => Qualification" button under "Synchronization".  After waiting a bit, I get the following error when I visit any page in the Qualification server:

com.thoughtworks.xstream.converters.ConversionException: Refusing to unmarshal securityRealm for security reasons; see https://jenkins.io/redirect/class-filter/
---- Debugging information ----
class : hudson.security.LDAPSecurityRealm
required-type : hudson.security.LDAPSecurityRealm
converter-type : hudson.util.XStream2$BlacklistedTypesConverter
path : /hudson/securityRealm
line number : 25
-------------------------------
at hudson.util.XStream2$BlacklistedTypesConverter.unmarshal(XStream2.java:546)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at hudson.util.RobustReflectionConverter.unmarshalField(RobustReflectionConverter.java:390)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:328)
Caused: jenkins.util.xstream.CriticalXStreamException: Refusing to unmarshal securityRealm for security reasons; see https://jenkins.io/redirect/class-filter/
---- Debugging information ----
class : hudson.security.LDAPSecurityRealm
required-type : hudson.security.LDAPSecurityRealm
converter-type : hudson.util.XStream2$BlacklistedTypesConverter
path : /hudson/securityRealm
line number : 25
------------------------------- : Refusing to unmarshal securityRealm for security reasons; see https://jenkins.io/redirect/class-filter/
---- Debugging information ----
class : hudson.security.LDAPSecurityRealm
required-type : hudson.security.LDAPSecurityRealm
converter-type : hudson.util.XStream2$BlacklistedTypesConverter
path : /hudson/securityRealm
line number : 25
-------------------------------
message : Refusing to unmarshal securityRealm for security reasons; see https://jenkins.io/redirect/class-filter/
---- Debugging information ----
class : hudson.security.LDAPSecurityRealm
required-type : hudson.security.LDAPSecurityRealm
converter-type : hudson.util.XStream2$BlacklistedTypesConverter
path : /hudson/securityRealm
line number : 25
-------------------------------
cause-exception : com.thoughtworks.xstream.converters.ConversionException
cause-message : Refusing to unmarshal securityRealm for security reasons; see https://jenkins.io/redirect/class-filter/
class : hudson.model.Hudson
required-type : hudson.security.LDAPSecurityRealm
converter-type : hudson.util.RobustReflectionConverter
path : /hudson/securityRealm
line number : 25
version : not available
-------------------------------
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:353)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:267)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1189)
at hudson.util.XStream2.unmarshal(XStream2.java:161)
at hudson.util.XStream2.unmarshal(XStream2.java:132)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1173)
at hudson.XmlFile.unmarshal(XmlFile.java:180)
Caused: java.io.IOException: Unable to read /net/www/ci/coq-qualif/config.xml
at hudson.XmlFile.unmarshal(XmlFile.java:183)
at hudson.XmlFile.unmarshal(XmlFile.java:163)
at jenkins.model.Jenkins.loadConfig(Jenkins.java:3118)
at jenkins.model.Jenkins.access$1200(Jenkins.java:320)
at jenkins.model.Jenkins$13.run(Jenkins.java:3219)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:1133)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused: org.jvnet.hudson.reactor.ReactorException
at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:282)
at jenkins.InitReactorRunner.run(InitReactorRunner.java:50)
at jenkins.model.Jenkins.executeReactor(Jenkins.java:1166)
at jenkins.model.Jenkins.<init>(Jenkins.java:966)
at hudson.model.Hudson.<init>(Hudson.java:85)
at hudson.model.Hudson.<init>(Hudson.java:81)
at hudson.WebAppMain$3.run(WebAppMain.java:233)
Caused: hudson.util.HudsonFailedToLoad
at hudson.WebAppMain$3.run(WebAppMain.java:250)