temporarily update with mimemagic fix

- tmp fix based on carrierwaveuploader#1934

carrierwave.gemspec

@@ -28,6 +28,8 @@ Gem::Specification.new do |s|
   s.add_dependency "activemodel", ">= 3.2.0"
   s.add_dependency "json", ">= 1.7"
   s.add_dependency "mime-types", ">= 1.16"
+  s.add_dependency "mimemagic", ">= 0.3.0"
+
   if RUBY_ENGINE == 'jruby'
     s.add_development_dependency 'activerecord-jdbcpostgresql-adapter'
   else

lib/carrierwave/sanitized_file.rb

@@ -2,6 +2,7 @@
 
 require 'pathname'
 require 'active_support/core_ext/string/multibyte'
+require 'mimemagic'
 
 begin
   # Use mime/types/columnar if available, for reduced memory usage
@@ -253,12 +254,10 @@ def to_file
     # [String] the content type of the file
     #
     def content_type
-      return @content_type if @content_type
-      if @file.respond_to?(:content_type) and @file.content_type
-        @content_type = @file.content_type.to_s.chomp
-      elsif path
-        @content_type = ::MIME::Types.type_for(path).first.to_s
-      end
+      @content_type ||=
+        existing_content_type ||
+        mime_magic_content_type ||
+        mime_types_content_type
     end
 
     ##
@@ -318,6 +317,22 @@ def sanitize(name)
       return name.mb_chars.to_s
     end
 
+    def existing_content_type
+      if @file.respond_to?(:content_type) && @file.content_type
+        @file.content_type.to_s.chomp
+      end
+    end
+
+    def mime_magic_content_type
+      MimeMagic.by_magic(File.open(path)).try(:type) if path
+    rescue Errno::ENOENT
+      nil
+    end
+
+    def mime_types_content_type
+      ::MIME::Types.type_for(path).first.to_s if path
+    end
+
     def split_extension(filename)
       # regular expressions to try for identifying extensions
       extension_matchers = [