Error on first run

I'm in the preview for a new AWS service, and have added the cli models for that service. I get the following error when running aws-shell.
```
$ aws-shell
First run, creating autocomplete index...
Traceback (most recent call last):
File "/usr/local/bin/aws-shell", line 9, in
load_entry_point('aws-shell==0.1.1', 'console_scripts', 'aws-shell')()
File "/Library/Python/2.7/site-packages/awsshell/__init__.py", line 47, in main
write_index(index_file)
File "/Library/Python/2.7/site-packages/awsshell/makeindex.py", line 67, in write_index
index_command(current, help_command)
File "/Library/Python/2.7/site-packages/awsshell/makeindex.py", line 59, in index_command
index_command(child, sub_help_command)
File "/Library/Python/2.7/site-packages/awsshell/makeindex.py", line 58, in index_command
sub_help_command = sub_command.create_help_command()
File "/Library/Python/2.7/site-packages/awscli/clidriver.py", line 514, in create_help_command
arg_table=self.arg_table,
File "/Library/Python/2.7/site-packages/awscli/clidriver.py", line 453, in arg_table
self._arg_table = self._create_argument_table()
File "/Library/Python/2.7/site-packages/awscli/clidriver.py", line 550, in _create_argument_table
input_shape = self._operation_model.input_shape
File "/Library/Python/2.7/site-packages/botocore/utils.py", line 522, in __get__
computed_value = self._fget(obj)
File "/Library/Python/2.7/site-packages/botocore/model.py", line 406, in input_shape
self._operation_model['input'])
File "/Library/Python/2.7/site-packages/botocore/model.py", line 246, in resolve_shape_ref
return self._shape_resolver.resolve_shape_ref(shape_ref)
File "/Library/Python/2.7/site-packages/botocore/model.py", line 507, in resolve_shape_ref
return self.get_shape_by_name(shape_ref['shape'])
File "/Library/Python/2.7/site-packages/botocore/model.py", line 485, in get_shape_by_name
raise NoShapeFoundError(shape_name)
botocore.model.NoShapeFoundError: NameOfApiCallForServiceInPreviewHere
```

I guess ideally the autocomplete indexer would just skip these cli models.