[PATCH] color: replace "purple_background" by "magenta_background"

[Denis Laxalde]

# HG changeset patch
# User Denis Laxalde <denis.laxalde at logilab.fr>
# Date 1476176128 -7200
#      Tue Oct 11 10:55:28 2016 +0200
# Node ID 1cf20c1c54cb8172816604de5e1d98d3cd62d711
# Parent  b85fa6bf298be07804a74d8fdec0d19fdbc6d740
# EXP-Topic color-purple-crash
color: replace "purple_background" by "magenta_background"

`hg debugcolor` crashes on my terminal:

      File "/usr/lib/python2.7/dist-packages/hgext/color.py", line 530, in debugcolor
        ui.write(('%s\n') % colors, label=label)
      File "/usr/lib/python2.7/dist-packages/hgext/color.py", line 446, in write
        *[self.label(a, label) for a in args], **opts)
      File "/usr/lib/python2.7/dist-packages/hgext/color.py", line 488, in label
        for s in msg.split('\n')])
      File "/usr/lib/python2.7/dist-packages/hgext/color.py", line 396, in render_effects
        for effect in ['none'] + effects.split())
      File "/usr/lib/python2.7/dist-packages/hgext/color.py", line 396, in <genexpr>
        for effect in ['none'] + effects.split())
      File "/usr/lib/python2.7/dist-packages/hgext/color.py", line 378, in _effect_str
        attr, val = _terminfo_params[effect]
    KeyError: 'purple'

Not sure where this "purple" comes (been there from initial file check in)
from but "magenta" seems more appropriate.

diff --git a/hgext/color.py b/hgext/color.py
--- a/hgext/color.py
+++ b/hgext/color.py
@@ -182,7 +182,7 @@ testedwith = 'ships-with-hg-core'
             'italic': 3, 'underline': 4, 'inverse': 7, 'dim': 2,
             'black_background': 40, 'red_background': 41,
             'green_background': 42, 'yellow_background': 43,
-            'blue_background': 44, 'purple_background': 45,
+            'blue_background': 44, 'magenta_background': 45,
             'cyan_background': 46, 'white_background': 47}
 
 def _terminfosetup(ui, mode):
@@ -591,7 +591,7 @@ else:
         'green_background': _BACKGROUND_GREEN,
         'yellow_background': _BACKGROUND_RED | _BACKGROUND_GREEN,
         'blue_background': _BACKGROUND_BLUE,
-        'purple_background': _BACKGROUND_BLUE | _BACKGROUND_RED,
+        'magenta_background': _BACKGROUND_BLUE | _BACKGROUND_RED,
         'cyan_background': _BACKGROUND_BLUE | _BACKGROUND_GREEN,
         'white_background': (_BACKGROUND_RED | _BACKGROUND_GREEN |
                              _BACKGROUND_BLUE),