[cleanup] Simplify date.dh_constVal function()

Change-Id: Ie8b6fb6ecc11a5d5362551b46775a8f209731734
---
M pywikibot/date.py
1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/pywikibot/date.py b/pywikibot/date.py
index 4f79f38..b2da643 100644
--- a/pywikibot/date.py
+++ b/pywikibot/date.py
@@ -226,18 +226,13 @@
 
     formats['CurrEvents']['en'](ind) => 'Current Events'
     formats['CurrEvents']['en']('Current Events') => ind
-
     """
     if isinstance(value, UnicodeType):
         if value == match:
             return ind
-        else:
-            raise ValueError()
-    else:
-        if value == ind:
-            return match
-        else:
-            raise ValueError('unknown value %d' % value)
+    elif value == ind:
+        return match
+    raise ValueError('unknown value {}'.format(value))
 
 
 def alwaysTrue(x):

