Refactor connection errors

Makes command.py a lot more readable.

fig/cli/errors.py

@@ -8,3 +8,46 @@ class UserError(Exception):
 
     def __unicode__(self):
         return self.msg
+
+
+class DockerNotFoundMac(UserError):
+    def __init__(self):
+        super(DockerNotFoundMac, self).__init__("""
+Couldn't connect to Docker daemon. You might need to install docker-osx:
+
+https://github.com/noplay/docker-osx
+""")
+
+
+class DockerNotFoundUbuntu(UserError):
+    def __init__(self):
+        super(DockerNotFoundUbuntu, self).__init__("""
+Couldn't connect to Docker daemon. You might need to install Docker:
+
+http://docs.docker.io/en/latest/installation/ubuntulinux/
+""")
+
+
+class DockerNotFoundGeneric(UserError):
+    def __init__(self):
+        super(DockerNotFoundGeneric, self).__init__("""
+Couldn't connect to Docker daemon. You might need to install Docker:
+
+http://docs.docker.io/en/latest/installation/
+""")
+
+
+class ConnectionErrorDockerOSX(UserError):
+    def __init__(self):
+        super(ConnectionErrorDockerOSX, self).__init__("""
+Couldn't connect to Docker daemon - you might need to run `docker-osx shell`.
+""")
+
+
+class ConnectionErrorGeneric(UserError):
+    def __init__(self, url):
+        super(ConnectionErrorGeneric, self).__init__("""
+Couldn't connect to Docker daemon at %s - is it running?
+
+If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.
+""" % url)