Add default path to Role & InstanceProfile

moto/iam/models.py

@@ -114,7 +114,7 @@ class Role(BaseModel):
         self.id = role_id
         self.name = name
         self.assume_role_policy_document = assume_role_policy_document
-        self.path = path
+        self.path = path or '/'
         self.policies = {}
         self.managed_policies = {}
 
@@ -166,7 +166,7 @@ class InstanceProfile(BaseModel):
     def __init__(self, instance_profile_id, name, path, roles):
         self.id = instance_profile_id
         self.name = name
-        self.path = path
+        self.path = path or '/'
         self.roles = roles if roles else []
 
     @classmethod