Address pytest warnings (#3629)

* Address `boto` deprecation warnings

This commit eliminates the following warning:

../boto/ec2/connection.py:582:
  PendingDeprecationWarning: The current get_all_instances implementation will be replaced with get_all_reservations.

`boto` isn't likely to ever make good on this warning, but doing the replacement will
declutter the `moto` test output.

* Remove `invoke_lambda` tracebacks from unit test logging

If an exception is encountered, the details are returned in the response payload.
Printing the traceback was just adding noise to the pytest output.

* Use known AMIs in unit tests

This commit eliminates the following warning in the pytest output:

`PendingDeprecationWarning: Could not find AMI with image-id:ami-123456, in the near future this will cause an error.`

Known, pre-loaded AMI image ids are used instead of random ids that don't actually
exist in the moto backend.  The integrity of the tests is unaffected by this change.

A test has been added to provide explicit coverage of the PendingDeprecationWarning
raised when an invalid AMI image id is passed to moto.

tests/test_ec2/test_instances.py

@@ -4,6 +4,7 @@ from __future__ import unicode_literals
 from botocore.exceptions import ClientError
 
 import pytest
+from unittest import SkipTest
 
 import base64
 import ipaddress
@@ -16,7 +17,7 @@ from boto.exception import EC2ResponseError
 from freezegun import freeze_time
 import sure  # noqa
 
-from moto import mock_ec2_deprecated, mock_ec2
+from moto import mock_ec2_deprecated, mock_ec2, settings
 from tests import EXAMPLE_AMI_ID
 from tests.helpers import requires_boto_gte
 
@@ -1664,3 +1665,15 @@ def test_describe_instance_attribute():
             invalid_instance_attribute=invalid_instance_attribute
         )
         ex.value.response["Error"]["Message"].should.equal(message)
+
+
+@mock_ec2
+def test_warn_on_invalid_ami():
+    if settings.TEST_SERVER_MODE:
+        raise SkipTest("Can't capture warnings in server mode.")
+    ec2 = boto3.resource("ec2", "us-east-1")
+    with pytest.warns(
+        PendingDeprecationWarning,
+        match=r"Could not find AMI with image-id:invalid-ami.+",
+    ):
+        ec2.create_instances(ImageId="invalid-ami", MinCount=1, MaxCount=1)