tiny refactor to nbconvert ansi filter

was looking at this code for another project, and was irked by what I
saw here, so just cleaned it up.

IPython/nbconvert/filters/ansi.py

@@ -39,16 +39,6 b' def strip_ansi(source):'
     return re.sub(r'\033\[(\d|;)+?m', '', source)
 
 
-def ansi2html(text):
-    """
-    Conver ansi colors to html colors.
-    
-    Parameters
-    ----------
-    text : str
-        Text containing ansi colors to convert to html
-    """
-    
     ansi_colormap = {
         '30': 'ansiblack',
         '31': 'ansired',
@@ -61,8 +51,6 b' def ansi2html(text):'
         '01': 'ansibold',
     }
 
-    # do ampersand first
-    text = text.replace('&', '&')
     html_escapes = {
         '<': '&lt;',
         '>': '&gt;',
@@ -70,11 +58,24 b' def ansi2html(text):'
         '"': '&quot;',
         '`': '&#96;',
     }
+ansi_re = re.compile('\x1b' + r'\[([\dA-Fa-f;]*?)m')
+
+def ansi2html(text):
+    """
+    Convert ansi colors to html colors.
+    
+    Parameters
+    ----------
+    text : str
+        Text containing ansi colors to convert to html
+    """
+
+    # do ampersand first
+    text = text.replace('&', '&amp;')
     
     for c, escape in html_escapes.items():
         text = text.replace(c, escape)
 
-    ansi_re = re.compile('\x1b' + r'\[([\dA-Fa-f;]*?)m')
     m = ansi_re.search(text)
     opened = False
     cmds = []
@@ -90,7 +91,7 b' def ansi2html(text):'
         classes = []
         for cmd in cmds:
             if cmd in ansi_colormap:
-                classes.append(ansi_colormap.get(cmd))
+                classes.append(ansi_colormap[cmd])
 
         if classes:
             opener = '<span class="%s">' % (' '.join(classes))