title: retrieve security groups using python boto but set vpc id
body: <p>i am trying to play around with python boto and i run the below example(below is the official doc for this).  I know for a fact that an SG called "Pub_HDP_SG" exist but when i try to run my command by passing in a parameter called groupnames i get below error.  I get the fact that this SG does not exist in my default VPC, so how do i set my VPC to a specific VPC ??    </p>
  
  <p><a href="http://boto.readthedocs.org/en/latest/ref/ec2.html?highlight=get_all_security_groups#boto.ec2.connection.EC2Connection.get_all_security_groups" rel="nofollow">http://boto.readthedocs.org/en/latest/ref/ec2.html?highlight=get_all_security_groups#boto.ec2.connection.EC2Connection.get_all_security_groups</a></p>
  
  <pre><code>&gt;&gt;&gt; import boto
  &gt;&gt;&gt; ec2 = boto.connect_ec2()
  &gt;&gt;&gt; sg = ec2.get_all_security_groups()
  &gt;&gt;&gt; print sg
  [SecurityGroup:default, SecurityGroup:Pub_HDP_SG, SecurityGroup:RDP Rule - open everyone , SecurityGroup:us-east-open-all, SecurityGroup:wordpress-app-SG, SecurityGroup:default, SecurityGroup:AWS-AMI-SG, SecurityGroup:launch-wizard-2]
  &gt;&gt;&gt;
  &gt;&gt;&gt; sgn = "Pub_HDP_SG"
  &gt;&gt;&gt;
  &gt;&gt;&gt; sg = ec2.get_all_security_groups(groupnames=[sgn])
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "/usr/lib/python2.6/site-packages/boto/ec2/connection.py", line 2968, in get_all_security_groups
      [('item', SecurityGroup)], verb='POST')
    File "/usr/lib/python2.6/site-packages/boto/connection.py", line 1186, in get_list
      raise self.ResponseError(response.status, response.reason, body)
  boto.exception.EC2ResponseError: EC2ResponseError: 400 Bad Request
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;Response&gt;&lt;Errors&gt;&lt;Error&gt;&lt;Code&gt;InvalidGroup.NotFound&lt;/Code&gt;&lt;Message&gt;The security group 'Pub_HDP_SG' does not exist in default VPC 'vpc-b3bf61d6'&lt;/Message&gt;&lt;/Error&gt;&lt;/Errors&gt;&lt;RequestID&gt;c708a4cd-0bc9-4761-a5a6-556b1c68ecdb&lt;/RequestID&gt;&lt;/Response&gt;
  &gt;&gt;&gt;
  </code></pre>