Remove boto package dependency

The `boto` library (long ago superseded by `boto3`) has not had an official
release in over two years or even a commit in the last 18 months.  Importing
the package (or indirectly importing it by via `moto`) generates a deprecation
warning.  Additionally, an ever-increasing number of `moto` users who have
left `boto` behind for `boto3` are still being forced to install `boto`.

This commit vendors a very small subset of the `boto` library--only the code
required by `moto` to run--into the /packages subdirectory.  A README file
is included explaining the origin of the files and a recommendation for how
they can be removed entirely in a future release.

NOTE: Users of `boto` will still be able to use `moto` after this is merged.

closes #2978
closes #3013
closes #3170
closes #3418

relates to #2950

moto/ec2/models.py

@@ -15,10 +15,15 @@ from pkg_resources import resource_filename
 from collections import defaultdict
 import weakref
 from datetime import datetime
-from boto.ec2.instance import Instance as BotoInstance, Reservation
-from boto.ec2.blockdevicemapping import BlockDeviceMapping, BlockDeviceType
-from boto.ec2.spotinstancerequest import SpotInstanceRequest as BotoSpotRequest
-from boto.ec2.launchspecification import LaunchSpecification
+from moto.packages.boto.ec2.instance import Instance as BotoInstance, Reservation
+from moto.packages.boto.ec2.blockdevicemapping import (
+    BlockDeviceMapping,
+    BlockDeviceType,
+)
+from moto.packages.boto.ec2.spotinstancerequest import (
+    SpotInstanceRequest as BotoSpotRequest,
+)
+from moto.packages.boto.ec2.launchspecification import LaunchSpecification
 
 from moto.compat import OrderedDict
 from moto.core import BaseBackend

moto/ec2/responses/instances.py

@@ -1,5 +1,5 @@
 from __future__ import unicode_literals
-from boto.ec2.instancetype import InstanceType
+from moto.packages.boto.ec2.instancetype import InstanceType
 
 from moto.autoscaling import autoscaling_backends
 from moto.core.responses import BaseResponse