AWS CLI exits successfully when unable to read from credentials file using `aws configuration get`

This is very easy to reproduce, and happened to me as a result of copying a credential file from another mount and not owning the file with my current user.

If for some reason, the user executing the aws command doesn't have file access to `~/.aws/credentials` the CLI will exit 0 and echo nothing. If it so happens that you do not define a `[profile ]` for a `[]` entry in ~/.aws/credentials AWS CLI cannot even see the values and gives you an error that the profile doesn't exist (it does).

Here is the fullest example I can produce:
```
➜ cosmos-hash-circuit git:(master) ✗ aws configure
AWS Access Key ID [None]: default_key
AWS Secret Access Key [None]: default_secret
Default region name [None]: us-east-1
Default output format [None]: json
➜ cosmos-hash-circuit git:(master) ✗ cat ~/.aws/config
[default]
output = json
region = us-east-1
➜ cosmos-hash-circuit git:(master) ✗ gvim ~/.aws/credentials
➜ cosmos-hash-circuit git:(master) ✗ sudo chown root:root ~/.aws/credentials
➜ cosmos-hash-circuit git:(master) ✗ sudo cat ~/.aws/credentials
[default]
aws_secret_access_key = default_secret
aws_access_key_id = default_key

[foo]
aws_secret_access_key = default_foo_secret
aws_access_key_id = default_foo_key
➜ cosmos-hash-circuit git:(master) ✗ aws configure get aws_access_key_id
➜ cosmos-hash-circuit git:(master) ✗ aws configure get aws_access_key_id --profile foo

The config profile (foo) could not be found
➜ cosmos-hash-circuit git:(master) ✗ aws configure get profile.foo.aws_access_key_id
➜ cosmos-hash-circuit git:(master) ✗ sudo aws configure get aws_access_key_id
default_key
➜ cosmos-hash-circuit git:(master) ✗ sudo aws configure get aws_access_key_id --profile foo
default_foo_key
➜ cosmos-hash-circuit git:(master) ✗
➜ cosmos-hash-circuit git:(master) ✗ sudo aws configure get profile.foo.aws_access_key_id
default_foo_key

```
It was pretty frustrating when I realized what the problem was the whole time. It would have been nice if the CLI simply told me that it could not read from the file.