Replace resource.txt with resource.robot

Change-Id: I4d2afd35645880e33a31644cd717bbeae55666f0
Signed-off-by: Sandhya Somashekar <sansomas@in.ibm.com>
diff --git a/tests/test_certificate.robot b/tests/test_certificate.robot
index 7ade544..3469418 100755
--- a/tests/test_certificate.robot
+++ b/tests/test_certificate.robot
@@ -3,7 +3,7 @@
 Documentation  Test certificate in OpenBMC.
 
 Resource       ../lib/rest_client.robot
-Resource       ../lib/resource.txt
+Resource       ../lib/resource.robot
 Resource       ../lib/openbmc_ffdc.robot
 Resource       ../lib/certificate_utils.robot