Ec2 InstanceExists waiter throws an exception immediately if the instance does not exist

[nicholasbishop]

Code that reproduces the issue:

import boto3
import botocore

print('boto3 version:', boto3.__version__)
print('botocore version:', botocore.__version__)

# This is an instance that does not exist
invalid_instance_id = 'i-12345678'

ec2_client = boto3.client('ec2')
waiter = ec2_client.get_waiter('instance_exists')
waiter.wait(InstanceIds=[invalid_instance_id])

(Note that although this is an artificial example with an obviously-fake instance ID, the issue also reproduces occasionally with real instances if the waiter is called immediately after creating the instance.)

Output:

$ python3 repro.py 
boto3 version: 1.3.1
botocore version: 1.4.15
Traceback (most recent call last):
  File "repro.py", line 12, in <module>
    waiter.wait(InstanceIds=[invalid_instance_id])
  File "/usr/lib/python3.4/site-packages/botocore/waiter.py", line 53, in wait
    Waiter.wait(self, **kwargs)
  File "/usr/lib/python3.4/site-packages/botocore/waiter.py", line 292, in wait
    if acceptor.matcher_func(response):
  File "/usr/lib/python3.4/site-packages/botocore/waiter.py", line 194, in acceptor_matches
    return expression.search(response) == expected
  File "/usr/lib/python3.4/site-packages/jmespath/parser.py", line 524, in search
    result = interpreter.visit(self.parsed, value)
  File "/usr/lib/python3.4/site-packages/jmespath/visitor.py", line 66, in visit
    return method(node, *args, **kwargs)
  File "/usr/lib/python3.4/site-packages/jmespath/visitor.py", line 114, in visit_comparator
    self.visit(node['children'][0], value),
  File "/usr/lib/python3.4/site-packages/jmespath/visitor.py", line 66, in visit
    return method(node, *args, **kwargs)
  File "/usr/lib/python3.4/site-packages/jmespath/visitor.py", line 129, in visit_function_expression
    return self._functions.call_function(node['value'], resolved_args)
  File "/usr/lib/python3.4/site-packages/jmespath/functions.py", line 89, in call_function
    self._validate_arguments(resolved_args, signature, function_name)
  File "/usr/lib/python3.4/site-packages/jmespath/functions.py", line 100, in _validate_arguments
    return self._type_check(args, signature, function_name)
  File "/usr/lib/python3.4/site-packages/jmespath/functions.py", line 107, in _type_check
    function_name)
  File "/usr/lib/python3.4/site-packages/jmespath/functions.py", line 122, in _type_check_single
    self._convert_to_jmespath_type(actual_typename), types)
jmespath.exceptions.JMESPathTypeError: In function length(), invalid type for value: None, expected one of: ['string', 'array', 'object'], received: "null"

Partial debug logging output (I wasn't sure if the log output could contain sensitive info, hopefully this portion is sufficient):

DEBUG:botocore.endpoint:Sending http request: <PreparedRequest [POST]>
INFO:botocore.vendored.requests.packages.urllib3.connectionpool:Starting new HTTPS connection (1): ec2.us-east-1.amazonaws.com
DEBUG:botocore.vendored.requests.packages.urllib3.connectionpool:"POST / HTTP/1.1" 400 None
DEBUG:botocore.parsers:Response headers: {'nncoection': 'close', 'transfer-encoding': 'chunked', 'date': 'Tue, 03 May 2016 04:53:17 GMT', 'server': 'AmazonEC2'}
DEBUG:botocore.parsers:Response body:
b'<?xml version="1.0" encoding="UTF-8"?>\n<Response><Errors><Error><Code>InvalidInstanceID.NotFound</Code><Message>The instance ID \'i-12345678\' does not exist</Message></Error></Errors><RequestID>67ae3003-e224-4a9e-b429-3d6b4d19ec6f</RequestID></Response>'

I believe the problem is in this acceptor: https://github.com/boto/botocore/blob/develop/botocore/data/ec2/2015-10-01/waiters-2.json#L9

It was changed in 23fd477#diff-7c69e2e0de75f54556bb554dea557950; it used to only look at the response status rather than the response body.

Reverting that change to the JSON fixes the problem in my environment.

[jamesls]

Confirmed bug. Taking a look at your PR now.