Add transparent support for colour on Windows

If the colorama package is present, we use that to provide support for
coloured output on Windows. Otherwise, we fall back to no colour.

honcho/printer.py

@@ -1,6 +1,7 @@
 from collections import namedtuple
 import sys
 
+from .compat import ON_WINDOWS
 
 Message = namedtuple("Message", "type data time name colour")
 
@@ -51,3 +52,16 @@ def _ansi(code):
 
 def _colour_string(colour, s):
     return '{0}{1}{2}'.format(_ansi(colour), s, _ansi(0))
+
+
+if ON_WINDOWS:
+    # The colorama package provides transparent support for ANSI colour codes
+    # on Win32 platforms. We try and import and configure that, but fall back
+    # to no colour if we fail.
+    try:
+        import colorama
+    except ImportError:
+        def _colour_string(colour, s):  # noqa
+            return s
+    else:
+        colorama.init()