title: No module named psycopg2 even after i installed psycopg2
body: <p>I have </p>
  
  <pre><code>#!/usr/bin/python3
  import psycopg2
  </code></pre>
  
  <p>in my first couple lines of the code. 
  However, it shows that </p>
  
  <pre><code>ImportError: No module named psycopg2
  </code></pre>
  
  <p>even after I install psycopg2</p>
  
  <p>Below is the detail errors from the ternimal. </p>
  
  <pre><code> 432p1:/vagrant&gt; pip3 install psycopg2
  Collecting psycopg2
    Downloading psycopg2-2.7.3.1-cp35-cp35m-manylinux1_x86_64.whl (2.6MB)
      100% |████████████████████████████████| 2.6MB 526kB/s 
  Installing collected packages: psycopg2
  Successfully installed psycopg2-2.6.1
  You are using pip version 8.1.1, however version 9.0.1 is available.
  You should consider upgrading via the 'pip install --upgrade pip' command.
  432p1:/vagrant&gt; ./test-example.py pys.py
  Traceback (most recent call last):
    File "./test-example.py", line 2, in &lt;module&gt;
      import psycopg2
  ImportError: No module named psycopg2
  432p1:/vagrant&gt; ./clean-example.py
  Traceback (most recent call last):
    File "./clean-example.py", line 2, in &lt;module&gt;
      import psycopg2
  ImportError: No module named psycopg2
  432p1:/vagrant&gt; 
  </code></pre>
  
  <p>In addition i tried to run import in my python console and there is no error, however,when i run the test it has error </p>
  
  <pre><code>432p1:/vagrant&gt; python3
  Python 3.5.2 (default, Aug 18 2017, 17:48:00) 
  [GCC 5.4.0 20160609] on linux
  Type "help", "copyright", "credits" or "license" for more information.
  &gt;&gt;&gt; import psycopg2
  &gt;&gt;&gt; ./test-example.py pys.py 
    File "&lt;stdin&gt;", line 1
      ./test-example.py pys.py 
      ^
  SyntaxError: invalid syntax
  &gt;&gt;&gt; 
  </code></pre>
  
  <p>Thanks</p>