Misleading UnboundLocalError exception

[Aratz]

In pyurdme.py (dev branch) from line 2289:

            try:
                if self.report_level >= 1:  #stderr & stdout to the terminal
                    handle = subprocess.Popen(urdme_solver_cmd)
                else:
                    handle = subprocess.Popen(urdme_solver_cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE)
                    stdout, stderr = handle.communicate()
                return_code = handle.wait()
            except OSError as e:
                print "Error, execution of solver raised an exception: {0}".format(e)
                print "urdme_solver_cmd = {0}".format(urdme_solver_cmd) #<-- This message should be forwarded as an exception

            if return_code != 0:
                if self.report_level >= 1:
                    try:
                        print stderr, stdout
                    except Exception as e:
                        pass
                print "urdme_solver_cmd = {0}".format(urdme_solver_cmd)
                raise URDMEError("Solver execution failed, return code = {0}".format(return_code))

If an exception is raised by the solver, "return_code" is never initialized which leads to an UnboundLocalError exception (which is misleading since the problem comes from the solver). OSError should be forwarded instead.