rm improper assert syntax

assert only raise AssertionError when runing python without '-O', so if
we except an Assertionerror in codes, just raise it instead of using
assert syntax instead of different result with or without '-O' flag

Change-Id: I8c1bc2c6849996f0d3f7a4b791671871d79dd939
Client V3 shouldn't inherit V2

Client V3 is a completely different implementation of the API, if we
want to intermix the V2 and V3 APIs then we don't need to version our
client at all.

Change-Id: I80579cd41df73ccfc6c8feb76843772829afac4e
Merge "rm improper assert syntax"
Merge "Client V3 shouldn't inherit V2"