Kernel.exec still failing in OS X Leopard [closes GH-544]

lib/vagrant/ssh.rb

@@ -53,9 +53,6 @@ module Vagrant
         command_options << "-o ForwardX11Trusted=yes"
       end
 
-      # Some hackery going on here. On Mac OS X Leopard (10.5), exec fails
-      # (GH-51). As a workaround, we fork and wait. On all other platforms,
-      # we simply exec.
       command = "ssh #{command_options.join(" ")} #{options[:username]}@#{options[:host]}".strip
       env.logger.info("ssh") { "Invoking SSH: #{command}" }
       safe_exec(command)

lib/vagrant/util/safe_exec.rb

@@ -2,7 +2,7 @@ module Vagrant
   module Util
     # This module provies a `safe_exec` method which is a drop-in
     # replacement for `Kernel.exec` which addresses a specific issue
-    # which manifests on OS X 10.5 and perhaps other operating systems.
+    # which manifests on OS X 10.5 (GH-51) and perhaps other operating systems.
     # This issue causes `exec` to fail if there is more than one system
     # thread. In that case, `safe_exec` automatically falls back to
     # forking.
@@ -14,6 +14,7 @@ module Vagrant
         rescue_from = []
         rescue_from << Errno::EOPNOTSUPP if defined?(Errno::EOPNOTSUPP)
         rescue_from << Errno::E045 if defined?(Errno::E045)
+        rescue_from << SystemCallError
 
         fork_instead = false
         begin