Wrap guess_cask_version with timeout.

Library/Homebrew/dev-cmd/bump-unversioned-casks.rb

@@ -126,7 +126,16 @@ module Homebrew
         onoe e
       end
 
-      if sha256.present? && last_sha256 != sha256 && (version = unversioned_cask_checker.guess_cask_version)
+      if sha256.present? && last_sha256 != sha256
+        version = begin
+          Timeout.timeout(1.minute) do
+            unversioned_cask_checker.guess_cask_version
+          end
+        rescue Timeout::Error
+          onoe "Timed out guessing version for cask '#{cask}'."
+        end
+
+        if version
           if cask.version == version
             oh1 "Cask #{cask} is up-to-date at #{version}"
           else
@@ -154,6 +163,7 @@ module Homebrew
           end
         end
       end
+    end
 
     {
       "sha256"     => sha256,