utils: add a pop_key helper function

pop_key removes a value from a dictionary and it in one step.
This function will be used in the next integration.

Signed-off-by: David Aguilar <davvid@gmail.com>

Author: davvid

lib/git_python/utils.py

@@ -3,3 +3,9 @@ def dashify(string):
 
 def touch(filename):
     open(filename, "a").close()
+
+def pop_key(d, key):
+    value = d.get(key, None)
+    if key in d:
+        del d[key]
+    return value