Fix #3552: linkcheck raises UnboundLocalError

CHANGES

@@ -67,6 +67,7 @@ Bugs fixed
 * #3450: &nbsp is appeared in EPUB docs
 * #3418: Search button is misaligned in nature and pyramid theme
 * #3421: Could not translate a caption of tables
+* #3552: linkcheck raises UnboundLocalError
 
 Release 1.5.2 (released Jan 22, 2017)
 =====================================

sphinx/builders/linkcheck.py

@@ -167,7 +167,9 @@ class CheckExternalLinksBuilder(Builder):
                 # history contains any redirects, get last
                 if response.history:
                     code = response.history[-1].status_code
-                return 'redirected', new_url, code
+                    return 'redirected', new_url, code
+                else:
+                    return 'redirected', new_url, 0
 
         def check():
             # check for various conditions without bothering the network