Can't find boto3

I have boto3 installed on my machine, but when I run the script I get an error about not finding boto3.

```
File "/usr/local/lib/python3.7/site-packages/locust/util/load_locustfile.py", line 58, in load_locustfile
imported = source.load_module()
File "", line 407, in _check_name_wrapper
File "", line 907, in load_module
File "", line 732, in load_module
File "", line 265, in _load_module_shim
File "", line 696, in _load
File "", line 677, in _load_unlocked
File "", line 728, in exec_module
File "", line 219, in _call_with_frames_removed
File "/home/ec2-user/SageMaker/Test/load-testing-sagemaker-endpoints/locust/locust_script.py", line 2, in
import boto3
ModuleNotFoundError: No module named 'boto3'
```