Installing nokogiri (1.5.2)
Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

        /usr/bin/ruby1.9.1 extconf.rb
extconf.rb:10: Use RbConfig instead of obsolete and deprecated Config.
checking for libxml/parser.h... yes
checking for libxslt/xslt.h... yes
checking for libexslt/exslt.h... yes
checking for iconv_open() in iconv.h... yes
checking for xmlParseDoc() in -lxml2... yes
checking for xsltParseStylesheetDoc() in -lxslt... yes
checking for exsltFuncRegister() in -lexslt... yes
checking for xmlHasFeature()... yes
checking for xmlFirstElementChild()... yes
checking for xmlRelaxNGSetParserStructuredErrors()... yes
checking for xmlRelaxNGSetParserStructuredErrors()... yes
checking for xmlRelaxNGSetValidStructuredErrors()... yes
checking for xmlSchemaSetValidStructuredErrors()... yes
checking for xmlSchemaSetParserStructuredErrors()... yes
creating Makefile

make
compiling xml_element_content.c
compiling html_sax_push_parser.c
compiling xml_node_set.c
xml_node_set.c: In function ‘dealloc_namespace’:
xml_node_set.c:9:13: warning: cast discards ‘__attribute__((const))’ qualifier from pointer target type [-Wcast-qual]
     xmlFree((xmlChar *)ns->href);
             ^
xml_node_set.c:11:13: warning: cast discards ‘__attribute__((const))’ qualifier from pointer target type [-Wcast-qual]
     xmlFree((xmlChar *)ns->prefix);
             ^
compiling xml_relax_ng.c
compiling html_document.c
compiling xml_element_decl.c
compiling xml_sax_push_parser.c
compiling xml_entity_decl.c
compiling xml_syntax_error.c
compiling xml_attr.c
compiling xml_attribute_decl.c
compiling xml_comment.c
compiling xml_namespace.c
xml_namespace.c: In function ‘prefix’:
xml_namespace.c:14:13: warning: variable ‘doc’ set but not used [-Wunused-but-set-variable]
   xmlDocPtr doc;
             ^
xml_namespace.c: In function ‘href’:
xml_namespace.c:33:13: warning: variable ‘doc’ set but not used [-Wunused-but-set-variable]
   xmlDocPtr doc;
             ^
compiling xml_entity_reference.c
compiling xml_reader.c
compiling xml_document_fragment.c
compiling xml_io.c
xml_io.c: In function ‘io_read_callback’:
xml_io.c:28:3: warning: conversion to ‘int’ from ‘size_t’ may alter its value [-Wconversion]
   return safe_len;
   ^
compiling html_entity_lookup.c
compiling xml_libxml2_hacks.c
compiling xml_sax_parser_context.c
compiling xml_encoding_handler.c
compiling xml_processing_instruction.c
compiling nokogiri.c
compiling xml_text.c
compiling xslt_stylesheet.c
compiling xml_sax_parser.c
compiling xml_node.c
compiling xml_xpath_context.c
xml_xpath_context.c: In function ‘xpath_generic_exception_handler’:
xml_xpath_context.c:189:3: error: format not a string literal and no format arguments [-Werror=format-security]
   rb_raise(rb_eRuntimeError, message);
   ^
cc1: some warnings being treated as errors
make: *** [xml_xpath_context.o] Error 1


Gem files will remain installed in /var/lib/gems/1.9.1/gems/nokogiri-1.5.2 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/nokogiri-1.5.2/ext/nokogiri/gem_make.out
An error occurred while installing nokogiri (1.5.2), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.5.2'` succeeds before bundling.