test: py: Add cmd_echo dependency

There is missing dependency on echo command. Mark tests which requires
echo.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
diff --git a/test/py/tests/test_env.py b/test/py/tests/test_env.py
index 035dbf5..b7f960c 100644
--- a/test/py/tests/test_env.py
+++ b/test/py/tests/test_env.py
@@ -164,6 +164,7 @@
     value = state_test_env.env[var]
     validate_set(state_test_env, var, value)
 
+@pytest.mark.buildconfigspec('cmd_echo')
 def test_env_echo_non_existent(state_test_env):
     """Test echoing a variable that doesn't exist."""
 
@@ -179,6 +180,7 @@
         response = c.run_command('printenv %s' % var)
     assert(response == '## Error: "%s" not defined' % var)
 
+@pytest.mark.buildconfigspec('cmd_echo')
 def test_env_unset_non_existent(state_test_env):
     """Test unsetting a nonexistent variable."""
 
@@ -202,6 +204,7 @@
     set_var(state_test_env, var, value)
     validate_set(state_test_env, var, value)
 
+@pytest.mark.buildconfigspec('cmd_echo')
 def test_env_unset_existing(state_test_env):
     """Test unsetting a variable."""