Use String::Affix token for string prefixes in Python lexer (#1635)

String prefixes were given the same token (`Str`) at the string itself.
This commit uses the `String::Affix` token for the prefix character.
This is consistent with the tokens used by Pygments. New styles for
`String::Affix` are also added.

Author: tancnle

lib/rouge/lexers/python.rb

@@ -115,7 +115,7 @@ def current_string
         # TODO: not in python 3
         rule %r/`.*?`/, Str::Backtick
         rule %r/([rfbu]{0,2})('''|"""|['"])/i do |m|
-          token Str
+          groups Str::Affix, Str
           current_string.register type: m[1].downcase, delim: m[2]
           push :generic_string
         end

lib/rouge/themes/base16.rb

@@ -67,6 +67,7 @@ def self.make_light!
       style Keyword::Declaration, :fg => :base09
 
       style Literal::String, :fg => :base0B
+      style Literal::String::Affix, :fg => :base0E
       style Literal::String::Regex, :fg => :base0C
 
       style Literal::String::Interpol,

lib/rouge/themes/bw.rb

@@ -26,6 +26,7 @@ class BlackWhiteTheme < CSSTheme
       style Name::Tag,                   :bold => true
 
       style Literal::String,             :italic => true
+      style Literal::String::Affix,      :bold => true
       style Literal::String::Interpol,   :bold => true
       style Literal::String::Escape,     :bold => true
 

lib/rouge/themes/colorful.rb

@@ -37,6 +37,7 @@ class Colorful < CSSTheme
       style Name::Decorator,             :fg => "#555", :bold => true
 
       style Literal::String,             :bg => "#fff0f0"
+      style Literal::String::Affix,      :fg => "#080", :bold => true
       style Literal::String::Char,       :fg => "#04D"
       style Literal::String::Doc,        :fg => "#D42"
       style Literal::String::Interpol,   :bg => "#eee"

lib/rouge/themes/github.rb

@@ -35,6 +35,7 @@ class Github < CSSTheme
       style Literal::Number::Integer,         :fg => '#009999'
       style Literal::Number::Oct,             :fg => '#009999'
       style Literal::Number,                  :fg => '#009999'
+      style Literal::String::Affix,           :fg => '#000000', :bold => true
       style Literal::String::Backtick,        :fg => '#d14'
       style Literal::String::Char,            :fg => '#d14'
       style Literal::String::Doc,             :fg => '#d14'

lib/rouge/themes/gruvbox.rb

@@ -150,6 +150,8 @@ def self.make_light!
             Literal::String::Interpol,
             Literal::String::Regex, :fg => :green, :italic => true
 
+      style Literal::String::Affix, :fg => :red
+
       style Literal::String::Escape, :fg => :orange
 
       style Name::Namespace,

lib/rouge/themes/igor_pro.rb

@@ -15,6 +15,7 @@ class IgorPro < CSSTheme
       style Keyword::Reserved,                :fg => '#007575'
       style Keyword,                          :fg => '#0000FF'
       style Literal::String,                  :fg => '#009C00'
+      style Literal::String::Affix,           :fg => '#0000FF'
       style Name::Builtin,                    :fg => '#C34E00'
     end
   end

lib/rouge/themes/magritte.rb

@@ -62,6 +62,7 @@ class Magritte < CSSTheme
             Literal::Date,                :fg => :forest, :bold => true
       style Literal::String::Symbol,      :fg => :forest
       style Literal::String,              :fg => :wine, :bold => true
+      style Literal::String::Affix,       :fg => :royal, :bold => true
       style Literal::String::Escape,
             Literal::String::Char,
             Literal::String::Interpol,    :fg => :purple, :bold => true

lib/rouge/themes/monokai.rb

@@ -59,6 +59,7 @@ class Monokai < CSSTheme
             Literal::Number::Oct,
             Literal::Number,
             Literal::String::Escape,          :fg => :light_violet
+      style Literal::String::Affix,           :fg => :soft_cyan, :bold => true
       style Literal::String::Backtick,
             Literal::String::Char,
             Literal::String::Doc,

lib/rouge/themes/pastie.rb

@@ -36,6 +36,7 @@ class Pastie < CSSTheme
       style Num,                       :fg => '#0000dd', :bold => true
 
       style Str,                       :fg => '#dd2200', :bg => '#fff0f0'
+      style Str::Affix,                :fg => '#008800', :bold => true
       style Str::Escape,               :fg => '#0044dd', :bg => '#fff0f0'
       style Str::Interpol,             :fg => '#3333bb', :bg => '#fff0f0'
       style Str::Other,                :fg => '#22bb22', :bg => '#f0fff0'