Fix TestTargetAPI.py test for users who use Swig 3.0.5 or greater.

DifferentialRevision: http://reviews.llvm.org/D13679
llvm-svn: 250188
diff --git a/lldb/scripts/interface/SBError.i b/lldb/scripts/interface/SBError.i
index d8dece2..bebf2d7 100644
--- a/lldb/scripts/interface/SBError.i
+++ b/lldb/scripts/interface/SBError.i
@@ -56,6 +56,7 @@
 checks that after calling the target.Launch() method there's no error
 condition and we get back a void process object.
 ") SBError;
+
 class SBError {
 public:
     SBError ();
@@ -94,6 +95,7 @@
     void
     SetErrorString (const char *err_str);
 
+    %varargs(3, char *str = NULL) SetErrorStringWithFormat;
     int
     SetErrorStringWithFormat (const char *format, ...);