No capabilities is not a power rule violation

pdbuddy/__init__.py

     seen_15v = False
     seen_20v = False
     seen_normative_voltages = False
-    if pdp <= 15:
+    if pdp == 0:
+        # No power is fine
+        seen_normative_voltages = True
+    elif pdp <= 15:
         # Below 15 W, make sure the PDP is available at 5 V.
         for pdo in pdo_list:
             if pdo.pdo_type == "fixed" and pdo.v == 5000:

test_pdbuddy/__init__.py

 
     def test_follows_power_rules_true(self):
         # <= 15 W
+        self.assertTrue(pdbuddy.follows_power_rules([]))
         self.assertTrue(pdbuddy.follows_power_rules([self.src_fixed_5v_1p5a]))
         self.assertTrue(pdbuddy.follows_power_rules([self.src_fixed_5v_3a]))
         self.assertTrue(pdbuddy.follows_power_rules([self.src_fixed_5v_3a,