Refactor command handling

This now supports usage/help texts

tests/packages/sshd/test_errors.py

@@ -83,8 +83,9 @@ class TestRegistrationErrors(BaseSshTests):
                 output = await process.stdout.readline()
                 assert "Enter public key" in output
                 stdout, stderr = await process.communicate(public_key)
+                assert isinstance(stderr, str)
                 print(f"{stdout=!r}, {stderr=!r}")
-                assert stderr == "Error: Invalid key type: Only RSA keys are supported."
+                assert stderr.rstrip() == "Error: Invalid key type: Only RSA keys are supported."
                 result = await process.wait()
                 assert result.exit_status == 1
 
@@ -102,8 +103,9 @@ class TestRegistrationErrors(BaseSshTests):
                 output = await process.stdout.readline()
                 assert "Enter public key" in output
                 stdout, stderr = await process.communicate(public_key)
+                assert isinstance(stderr, str)
                 print(f"{stdout=!r}, {stderr=!r}")
-                assert stderr == "Error: Invalid key type: Only RSA keys are supported."
+                assert stderr.rstrip() == "Error: Invalid key type: Only RSA keys are supported."
                 result = await process.wait()
                 assert result.exit_status == 1
 
@@ -122,7 +124,8 @@ class TestCommandErrors(BaseSshTests):
 
         assert result.exit_status == 1
         stderr = result.stderr or ""
-        assert stderr == "Error: Unsupported command."
+        assert isinstance(stderr, str)
+        assert stderr.rstrip() == "Error: Unsupported command."
 
     @pytest.mark.asyncio
     async def test_no_command(
@@ -136,7 +139,8 @@ class TestCommandErrors(BaseSshTests):
             async with conn.create_process() as process:
                 stdout, stderr = await process.communicate()
                 print(f"{stdout=!r}, {stderr=!r}")
-                assert stderr == "Error: No command was received from the client."
+                assert isinstance(stderr, str)
+                assert stderr.rstrip() == "Error: No command was received from the client."
                 result = await process.wait()
                 assert result.exit_status == 1