title: os.environ.get() does not return the Environment Value in windows?
body: <p>I already set SLACK_TOKEN environment Variable. But  <code>"SLACK_TOKEN=os.environ.get('SLACK_TOKEN')"</code> is returning "None".
  The type of <strong>SLACK_TOKEN</strong> is <strong>NoneType</strong>. I think os.environ.get not fetching value of environment variable. so rest of the code is not executing.</p>
  
  <pre><code>import os
  from slackclient import SlackClient
  
  
  SLACK_TOKEN= os.environ.get('SLACK_TOKEN') #returning None
  print(SLACK_TOKEN) # None
  print(type(SLACK_TOKEN)) # NoneType class
  
  slack_client = SlackClient(SLACK_TOKEN)
  print(slack_client.api_call("api.test")) #{'ok': True}
  print(slack_client.api_call("auth.test")) #{'ok': False, 'error': 'not_authed'}
  
  
  def list_channels():
      channels_call = slack_client.api_call("channels.list")
      if channels_call['ok']:
          return channels_call['channels']
      return None
  
  def channel_info(channel_id):
      channel_info = slack_client.api_call("channels.info", channel=channel_id)
      if channel_info:
          return channel_info['channel']
      return None
  
  if __name__ == '__main__':
      channels = list_channels()
      if channels:
          print("Channels: ")
          for c in channels:
              print(c['name'] + " (" + c['id'] + ")")
              detailed_info = channel_info(c['id'])
              if detailed_info:
                  print(detailed_info['latest']['text'])
      else:
          print("Unable to authenticate.") #Unable to authenticate
  </code></pre>