Add the possibility to color a source code SUBSTRING

`echo "There is an error in 'static void Functor::operator()( EOT& indiv ) { return indiv; }' you should fix it" | colout "'(.*)'" Cpp monokai`

README.md

@@ -36,7 +36,7 @@ When not specified, a *COLOR* defaults to _red_ and a *STYLE* defaults to _bold_
 (see the `-t` switch below).
 
 If the python-pygments library is available, `colout` can be used as an interface
-to it (see the `-s` switch below).
+to it (see also the `-s` switch below).
 
 `colout` is released under the GNU Public License v3.
 
@@ -124,3 +124,6 @@ special characters that would be recognize by your shell.
 * Color a JSON stream:
   `echo '{"foo": "lorem", "bar":"ipsum"}' | python -mjson.tool | colout -t json`
 
+* Color a source code substring:
+  `echo "There is an error in 'static void Functor::operator()( EOT& indiv ) { return indiv; }' you should fix it" | colout "'(.*)'" Cpp monokai`
+

colout.py

@@ -80,9 +80,8 @@ def colorin(text, color="red", style="normal"):
     if style == "random" or style == "Random":
         style = random.choice(list(styles.keys()))
     else:
-        assert(style in styles)
-
-    style_code = str(styles[style])
+        if style in styles:
+            style_code = str(styles[style])
 
     if color == "random":
         mode = 8
@@ -125,6 +124,24 @@ def colorin(text, color="red", style="normal"):
         mode = 8
         color_code = str(30 + colors[color])
 
+    # programming language
+    elif color.lower() in lexers:
+        lexer = get_lexer_by_name(color.lower())
+        # Python => 256 colors, python => 8 colors
+        ask_256 = color[0].isupper()
+        if ask_256:
+            try:
+                formatter = Terminal256Formatter(style=style)
+            except:  # style not found
+                formatter = Terminal256Formatter()
+        else:
+            if style not in ("light","dark"):
+                style = "dark" # dark color scheme by default
+            formatter = TerminalFormatter(bg=style)
+            # We should return all but the last character,
+            # because Pygments adds a newline char.
+        return highlight(text, lexer, formatter)[:-1]
+
     # 256 colors mode
     else:
         mode = 256