CDRIVER-4150 fix the AWS ECS test tasks (#1073)

* Use a Python virtual environment with upgraded boto3.

* Use separate client in shell auth.

* remove duplicate errexit

Author: kevinAlbs

.evergreen/config.yml

@@ -752,12 +752,12 @@ functions:
       working_dir: mongoc
       shell: bash
       script: |-
-        set -o errexit
         set -o errexit
         # Export the variables we need to construct URIs
         set +o xtrace
         export IAM_AUTH_ECS_ACCOUNT=${iam_auth_ecs_account}
         export IAM_AUTH_ECS_SECRET_ACCESS_KEY=${iam_auth_ecs_secret_access_key}
+        . ../drivers-evergreen-tools/.evergreen/auth_aws/activate_venv.sh
         sh ./.evergreen/run-aws-tests.sh ${TESTCASE}
   clone drivers-evergreen-tools:
   - command: shell.exec

.evergreen/ecs_hosted_test.js

@@ -33,8 +33,12 @@ TestData = {};
     const smoke = runMongoProgram(program, uri);
     assert.eq(smoke, 0, "Could not auth");
 
-    // Try the auth function
-    assert(external.auth({mechanism: 'MONGODB-AWS'}));
+    // Try the auth function on a new client.
+    (function () {
+        const conn = Mongo("mongodb://127.0.0.1:20000");
+        const external = conn.getDB("$external");
+        assert(external.auth({mechanism: 'MONGODB-AWS'}));
+    }());
 
     MongoRunner.stopMongod(conn);
 }());

build/evergreen_config_lib/functions.py

@@ -542,11 +542,11 @@
         EOF
         ''', silent=True),
         shell_mongoc(r'''
-        set -o errexit
         # Export the variables we need to construct URIs
         set +o xtrace
         export IAM_AUTH_ECS_ACCOUNT=${iam_auth_ecs_account}
         export IAM_AUTH_ECS_SECRET_ACCESS_KEY=${iam_auth_ecs_secret_access_key}
+        . ../drivers-evergreen-tools/.evergreen/auth_aws/activate_venv.sh
         sh ./.evergreen/run-aws-tests.sh ${TESTCASE}
         ''')
     )),