Pass size of the external tty into the container

Workaround the issue in Docker where the terminal has a strange size:
moby/moby#35407

This issue is purportedly fixed but I'm still seeing it.

cdflow.py

@@ -201,6 +201,10 @@ def docker_run(
                 'mode': 'ro',
             }
         if _command(command) == 'shell':
+            columns = int(check_output(['tput', 'cols']))
+            lines = int(check_output(['tput', 'lines']))
+            environment_variables['COLUMNS'] = columns
+            environment_variables['LINES'] = lines
             container = docker_client.containers.create(
                 image_id,
                 command=command,

test/test_docker.py

@@ -1,6 +1,7 @@
 import unittest
 from hashlib import sha256
 from string import printable
+from copy import deepcopy
 
 import docker
 from docker.client import DockerClient
@@ -244,7 +245,10 @@ def test_run_shell_command(self, fixtures):
         }
         docker_client.containers.create.return_value = container
 
-        with patch('cdflow.dockerpty') as dockerpty:
+        with patch('cdflow.dockerpty') as dockerpty, patch(
+            'cdflow.check_output',
+        ) as check_output:
+            check_output.return_value = '42\n'
             exit_status, output = docker_run(
                 docker_client,
                 image_id,
@@ -260,10 +264,14 @@ def test_run_shell_command(self, fixtures):
         assert exit_status == 0
         assert output == 'Shell end'
 
+        expected_environment_variable = deepcopy(environment_variables)
+        expected_environment_variable['COLUMNS'] = 42
+        expected_environment_variable['LINES'] = 42
+
         docker_client.containers.create.assert_called_once_with(
             image_id,
             command=command,
-            environment=environment_variables,
+            environment=expected_environment_variable,
             volumes={
                 project_root: {
                     'bind': project_root,