There is no az command in virutalenv bin folder after run azdev setup on Ubuntu

**Environment:**
Ubuntu 18.04

**Steps:**
1. setup python3.6 virtual env
> python3.6 -m venv py36
source py36/bin/activate

2. clone azure-cli
> git clone

3. install azdev and setup
> pip install azdev
azdev setup -c

**Expected:**
There should be a `az` command in py36/bin folder just as Windows/Mac do

**Actual:**
No `az` command found