Update docker commands. (#940)

* Add: Tests for newer version docker support.

* Add: Support for newer versions of docker (Modified rules.docker_not_command).

* Fix: Updated disabling memoize.

* Change: removed empty list check.

* Fix: _parse_commands now uses line.strip() internally and ends_with arg now doesn't end with newline.

* Change: Replaced disable_memoize in favor of no_memoize fixture.

* Fix: removed unused import.

thefuck/rules/docker_not_command.py

@@ -8,16 +8,30 @@ from thefuck.specific.sudo import sudo_support
 @sudo_support
 @for_app('docker')
 def match(command):
-    return 'is not a docker command' in command.output
+    return 'is not a docker command' in command.output or 'Usage:	docker' in command.output
+
+
+def _parse_commands(lines, starts_with):
+    lines = dropwhile(lambda line: not line.startswith(starts_with), lines)
+    lines = islice(lines, 1, None)
+    lines = list(takewhile(lambda line: line.strip(), lines))
+    return [line.strip().split(' ')[0] for line in lines]
 
 
 def get_docker_commands():
-    proc = subprocess.Popen('docker', stdout=subprocess.PIPE)
-    lines = [line.decode('utf-8') for line in proc.stdout.readlines()]
-    lines = dropwhile(lambda line: not line.startswith('Commands:'), lines)
-    lines = islice(lines, 1, None)
-    lines = list(takewhile(lambda line: line != '\n', lines))
-    return [line.strip().split(' ')[0] for line in lines]
+    proc = subprocess.Popen('docker', stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+
+    # Old version docker returns its output to stdout, while newer version returns to stderr.
+    lines = proc.stdout.readlines() or proc.stderr.readlines()
+    lines = [line.decode('utf-8') for line in lines]
+
+    # Only newer versions of docker have management commands in the help text.
+    if 'Management Commands:\n' in lines:
+        management_commands = _parse_commands(lines, 'Management Commands:')
+    else:
+        management_commands = []
+    regular_commands = _parse_commands(lines, 'Commands:')
+    return management_commands + regular_commands
 
 
 if which('docker'):
@@ -26,6 +40,10 @@ if which('docker'):
 
 @sudo_support
 def get_new_command(command):
+    if 'Usage:' in command.output and len(command.script_parts) > 1:
+        management_subcommands = _parse_commands(command.output.split('\n'), 'Commands:')
+        return replace_command(command, command.script_parts[2], management_subcommands)
+
     wrong_command = re.findall(
         r"docker: '(\w+)' is not a docker command.", command.output)[0]
     return replace_command(command, wrong_command, get_docker_commands())