regex password validation fails when invited

1. install nuxeo 7.10
2. add the following contribution:

   <require>org.nuxeo.ecm.platform.usermanager.UserManagerImpl</require>
   
   <extension target="org.nuxeo.ecm.platform.usermanager.UserService" point="userManager">
     <userManager>
   		      <!-- The password is valid if :
   			        - it has only word characters : [a-zA-Z0-9_]
   			        - it's at least 8 long
   			        - it has at least one digit
   			        - it has at least two lowercase letter
   			        - it has at least one uppercase letter -->
       <userPasswordPattern>
         ^\w*(?=.{8,})(?=.*\d)(?=(.*[a-z]){2,})(?=.*[A-Z])\w*$
       </userPasswordPattern>
     </userManager>
   </extension>
   
   <extension target="org.nuxeo.runtime.ConfigurationService" point="configuration">
     <property name="nuxeo.usermanager.check.password">true</property>
   </extension>
   

   following NXP-18751 implementation.

3. create a user without password
4. this generates a registration mail
5. click the link in the mail and enter a password which does not match the regex (password for instance)
6. observe the following stack in the logs:

   2018-01-26 11:48:31,747 ERROR [http-bio-0.0.0.0-8080-exec-27] [org.nuxeo.ecm.core.event.impl.EventServiceImpl] Exception during invitationListener sync listener execution, transaction will be rolled back
   org.nuxeo.ecm.platform.usermanager.exceptions.InvalidPasswordException: Unable to complete registration, null
   	at org.nuxeo.ecm.platform.usermanager.UserManagerImpl.checkPasswordValidity(UserManagerImpl.java:1262)
   	at org.nuxeo.ecm.platform.usermanager.UserManagerImpl.createUser(UserManagerImpl.java:1235)
   	at org.nuxeo.ecm.platform.usermanager.UserManagerImpl.createUser(UserManagerImpl.java:814)
   	at org.nuxeo.ecm.user.invite.DefaultInvitationUserFactory.doCreateUser(DefaultInvitationUserFactory.java:70)
   	at org.nuxeo.ecm.user.invite.UserInvitationComponent.createUser(UserInvitationComponent.java:729)
   	at org.nuxeo.ecm.user.invite.UserInvitationListener.handleEvent(UserInvitationListener.java:50)
   	at org.nuxeo.ecm.core.event.impl.EventServiceImpl.fireEvent(EventServiceImpl.java:191)
   	at org.nuxeo.ecm.user.invite.UserInvitationComponent.sendEvent(UserInvitationComponent.java:433)
   	at org.nuxeo.ecm.user.invite.UserInvitationComponent$RegistrationAcceptator.run(UserInvitationComponent.java:391)
   	at org.nuxeo.ecm.core.api.UnrestrictedSessionRunner.runUnrestricted(UnrestrictedSessionRunner.java:139)
   	at org.nuxeo.ecm.user.invite.UserInvitationComponent.validateRegistration(UserInvitationComponent.java:647)
   	at org.nuxeo.ecm.webengine.invite.UserInvitationObject.validateTrialForm(UserInvitationObject.java:94)
   	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
   	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   	at java.lang.reflect.Method.invoke(Method.java:498)
   	at com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
   	at com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ObjectOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:258)
   	at com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
   	at com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:302)
   	at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
   	at com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
   	at com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
   	at com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
   	at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1542)
   	at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1473)
   	at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1419)
   

Please note doing the same in 9.10 does not even enforce the format set by the regex.