Remove `None` entries on execute command

Signed-off-by: Ulysses Souza <ulyssessouza@gmail.com>

compose/cli/main.py

@@ -1466,7 +1466,12 @@ def call_docker(args, dockeropts, environment):
     args = [executable_path] + tls_options + args
     log.debug(" ".join(map(pipes.quote, args)))
 
-    return subprocess.call(args, env=environment)
+    filtered_env = {}
+    for k, v in environment.items():
+        if v is not None:
+            filtered_env[k] = environment[k]
+
+    return subprocess.call(args, env=filtered_env)
 
 
 def parse_scale_args(options):

tests/acceptance/cli_test.py

@@ -1711,6 +1711,17 @@ services:
         assert stderr == ""
         assert stdout == "/\n"
 
+    @mock.patch.dict(os.environ)
+    def test_exec_novalue_var_dotenv_file(self):
+        os.environ['MYVAR'] = 'SUCCESS'
+        self.base_dir = 'tests/fixtures/exec-novalue-var'
+        self.dispatch(['up', '-d'])
+        assert len(self.project.containers()) == 1
+
+        stdout, stderr = self.dispatch(['exec', '-T', 'nginx', 'env'])
+        assert 'CHECK_VAR=SUCCESS' in stdout
+        assert not stderr
+
     def test_exec_detach_long_form(self):
         self.base_dir = 'tests/fixtures/links-composefile'
         self.dispatch(['up', '--detach', 'console'])

tests/fixtures/exec-novalue-var/docker-compose.yml

@@ -0,0 +1,6 @@
+version: '3'
+services:
+  nginx:
+    image: nginx
+    environment:
+      - CHECK_VAR=${MYVAR}