Improve readability by extracting code

Only looking over the code did I see that there already exists a charm
store and so we should make it easier for others reading this to see
that this exists along with charm hub. Extracting the contents into
another file shows this.

This is a mechanical change that helps with readability, nothing else.

Author: SimonRichardson

juju/model.py

@@ -15,15 +15,13 @@
 from pathlib import Path
 
 import yaml
-
-import theblues.charmstore
-import theblues.errors
 import websockets
 
 from . import provisioner, tag, utils
 from .annotationhelper import _get_annotations, _set_annotations
 from .bundle import BundleHandler, get_charm_series
 from .charmhub import CharmHub
+from .charmstore import CharmStore
 from .client import client, connector
 from .client.client import ConfigValue, Value
 from .client.overrides import Caveat, Macaroon
@@ -461,6 +459,8 @@ def __init__(
         self._watch_stopped = asyncio.Event(loop=self._connector.loop)
         self._watch_received = asyncio.Event(loop=self._connector.loop)
         self._watch_stopped.set()
+
+        self._charmhub = CharmHub(self)
         self._charmstore = CharmStore(self._connector.loop)
 
     def is_connected(self):
@@ -783,7 +783,11 @@ def charmhub(self):
         the charm-hub-url model config.
 
         """
-        return CharmHub(self)
+        return self._charmhub
+
+    @property
+    def charmstore(self):
+        return self._charmstore
 
     async def get_info(self):
         """Return a client.ModelInfo object for this Model.
@@ -1968,10 +1972,6 @@ def upload_backup(self, archive_path):
         """
         raise NotImplementedError()
 
-    @property
-    def charmstore(self):
-        return self._charmstore
-
     async def get_metrics(self, *tags):
         """Retrieve metrics.
 
@@ -2186,38 +2186,6 @@ def _create_consume_args(offer, macaroon, controller_info):
     return arg
 
 
-class CharmStore:
-    """
-    Async wrapper around theblues.charmstore.CharmStore
-    """
-    def __init__(self, loop, cs_timeout=20):
-        self.loop = loop
-        self._cs = theblues.charmstore.CharmStore(timeout=cs_timeout)
-
-    def __getattr__(self, name):
-        """
-        Wrap method calls in coroutines that use run_in_executor to make them
-        async.
-        """
-        attr = getattr(self._cs, name)
-        if not callable(attr):
-            wrapper = partial(getattr, self._cs, name)
-            setattr(self, name, wrapper)
-        else:
-            async def coro(*args, **kwargs):
-                method = partial(attr, *args, **kwargs)
-                for attempt in range(1, 4):
-                    try:
-                        return await self.loop.run_in_executor(None, method)
-                    except theblues.errors.ServerError:
-                        if attempt == 3:
-                            raise
-                        await asyncio.sleep(1, loop=self.loop)
-            setattr(self, name, coro)
-            wrapper = coro
-        return wrapper
-
-
 class CharmArchiveGenerator:
     """
     Create a Zip archive of a local charm directory for upload to a controller.