Error message from exception.log is: 

2013-12-27 22:53:15 deployment-apache33 enwiki: [f9bc37e3] /w/api.php   Exception from line 3585 of /data/project/apache/common-local/php-master/includes/parser/Parser.php: Tag hook for namespace is not callable

#0 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3333): Parser->callParserFunction(Object(PPTemplateFrame_DOM), 'NAMESPACE', Array)
#1 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPTemplateFrame_DOM))
#2 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3247): PPFrame_DOM->expand(Object(PPNode_DOM))
#3 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPTemplateFrame_DOM))
#4 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3483): PPFrame_DOM->expand(Object(PPNode_DOM))
#5 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPTemplateFrame_DOM))
#6 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1532): PPFrame_DOM->expand(Object(DOMElement), 4)
#7 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1540): PPTemplateFrame_DOM->getNamedArgument('group allowed')
#8 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3947): PPTemplateFrame_DOM->getArgument('group allowed')
#9 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1132): Parser->argSubstitution(Array, Object(PPTemplateFrame_DOM))
#10 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3247): PPFrame_DOM->expand(Object(PPNode_DOM))
#11 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPTemplateFrame_DOM))
#12 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3247): PPFrame_DOM->expand(Object(PPNode_DOM))
#13 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPTemplateFrame_DOM))
#14 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3488): PPFrame_DOM->expand(Object(PPNode_DOM))
#15 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPTemplateFrame_DOM))
#16 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3483): PPFrame_DOM->expand(Object(PPNode_DOM))
#17 /data/project/apache/common-local/php-master/includes/parser/Preprocessor_DOM.php(1113): Parser->braceSubstitution(Array, Object(PPFrame_DOM))
#18 /data/project/apache/common-local/php-master/includes/parser/Parser.php(3150): PPFrame_DOM->expand(Object(PPNode_DOM), 0)
#19 /data/project/apache/common-local/php-master/includes/parser/Parser.php(1212): Parser->replaceVariables('{{editnotice lo...')
#20 /data/project/apache/common-local/php-master/includes/parser/Parser.php(395): Parser->internalParse('{{editnotice lo...')
#21 /data/project/apache/common-local/php-master/includes/cache/MessageCache.php(1064): Parser->parse('{{editnotice lo...', Object(Title), Object(ParserOptions), true)
#22 /data/project/apache/common-local/php-master/includes/Message.php(845): MessageCache->parse('{{editnotice lo...', NULL, true, true, Object(StubUserLang))
#23 /data/project/apache/common-local/php-master/includes/Message.php(590): Message->parseText('{{editnotice lo...')
#24 /data/project/apache/common-local/php-master/includes/Message.php(669): Message->toString()
#25 /data/project/apache/common-local/php-master/includes/Title.php(4892): Message->parseAsBlock()
#26 /data/project/apache/common-local/php-master/extensions/VisualEditor/ApiVisualEditor.php(298): Title->getEditNotices()
#27 /data/project/apache/common-local/php-master/includes/api/ApiMain.php(862): ApiVisualEditor->execute()
#28 /data/project/apache/common-local/php-master/includes/api/ApiMain.php(387): ApiMain->executeAction()
#29 /data/project/apache/common-local/php-master/includes/api/ApiMain.php(358): ApiMain->executeActionWithErrorHandling()
#30 /data/project/apache/common-local/php-master/api.php(76): ApiMain->execute()
#31 /data/project/apache/common-local/w/api.php(3): require('/data/project/a...')
#32 {main}