[Rivet] [PATCH] rivet-cmphisto: Fix PLOT:RatioPlotYLabel="..."

[Johann Felix v. Soden-Fraunhofen]

This change prevents overwritting RatioPlotYLabel if it is already 
set via PLOT:RatioPlotYLabel="...".

diff -r dbc5698ff208 bin/rivet-cmphistos
--- a/bin/rivet-cmphistos	Sat Dec 19 20:36:22 2015 +0000
+++ b/bin/rivet-cmphistos	Sat Jan 30 11:29:58 2016 +0100
@@ -429,7 +429,7 @@
         if showratio and len(varlines + mainlines) > 1:
             plot['RatioPlot'] = '1'
             plot['RatioPlotReference'] = ratioreference
-            if not hasdataref:
+            if not hasdataref and not plot.has_key("RatioPlotYLabel"):
                 if plot.get('RatioPlotMode', '') == 'deviation':
                     plot['RatioPlotYLabel'] = 'Deviation' #r'$\text{MC}-\text{MC}_\text{ref}$'
                 else: