Added logging of error rsync output if exists

Change-Id: I13c22219ab5f5d1377cd794d88cb94d57dedda98
diff --git a/trsync/utils/shell.py b/trsync/utils/shell.py
index 79a4f8b..c532be6 100644
--- a/trsync/utils/shell.py
+++ b/trsync/utils/shell.py
@@ -35,6 +35,8 @@
                                    stderr=subprocess.PIPE,
                                    shell=True)
         out, err = process.communicate()
+        if err:
+            self.logger.error(err)
         self.logger.debug(out)
         exitcode = process.returncode
         if process.returncode != 0 and raise_error: