_.string.find() problem

My Code:

<dtml-try>
<dtml-call procedure_assessment_new_entry>
<dtml-except DatabaseError>
<dtml-if expr="_.['error_value'].find('IDX_ERA_NUM')>0">
There is a record already present with ERA NUM <dtml-var era_num>.
</dtml-if>

<dtml-call "REQUEST.set('varDatabaseError','True')">
</dtml-try>


This produces the following Error:
Error Type: AttributeError
Error Value: DatabaseError instance has no attribute 'find'

Anybody able to help me fix this?

Thanks.