boto not using the temporary IAM credentials contained in EC2 instance metadata

[danielchalef]

boto, when called by odo, is not using the temporary IAM credentials contained in EC2 instance metadata and fails with an authentication error when attempting to access S3.

Steps to reproduce:

1. Attach an EC2 Role with 'AmazonS3FullAccess' permissions to an EC2 instance.
2. Start python from shell running in EC2 instance, and use boto to list the AWS account's associated buckets:

>>> import boto
>>> c = boto.connect_s3()
>>> rs = c.get_all_buckets()
>>> rs

This succeeds.
[<Bucket: ... >]
3. Attempt to load a CSV file in S3 into a pandas dataframe:

>>> df = odo('s3://.../dummy_data.csv', pd.DataFrame)

yields

...
boto.exception.S3ResponseError: S3ResponseError: 403 Forbidden
...

It appears that, when called from odo, boto is not using the temporary IAM credentials contained in the EC2 instance metadata.