refactor: Address review comments on #100

.github/workflows/check.yaml

@@ -72,7 +72,6 @@ jobs:
       - name: external controller juju config
         run: |
           mkdir -p $HOME/.local/share/juju
-          # TODO: can we remove the base64 encoding?
           echo ${{ secrets.JUJU_CONTROLLERS_YAML }} | base64 -d > $HOME/.local/share/juju/controllers.yaml
           echo ${{ secrets.JUJU_ACCOUNTS_YAML }} | base64 -d > $HOME/.local/share/juju/accounts.yaml
 
@@ -95,7 +94,7 @@ jobs:
 
       - name: install external controller required packages
         run: |
-           sudo snap install charmcraft --channel 2.x/stable --classic
+           sudo snap install charmcraft --channel 3.x/stable --classic
            sudo snap install juju --channel 3.4/stable --classic
            sudo --preserve-env=http_proxy,https_proxy,no_proxy pip3 install tox
            juju switch soleng-ci-ctrl-34

charmcraft.yaml

@@ -69,6 +69,8 @@ config:
         The charmed-openstack-exporter snap is by default installed from the latest/stable channel.
         This option allows the selection of a different channel.
 
+        In case the openStack-exporter resource has been attached, this option has no effect.
+
 
 links:
   documentation: https://discourse.charmhub.io/t/openstack-exporter-docs-index/13876
@@ -89,3 +91,5 @@ resources:
       scraping. The snap resource on Charmhub is intended to be an empty file. The charm will
       ignore an empty file resource and normally install the snap from the snap store, but a
       custom snap can also be provided here if needed.
+
+      This resource has top priority when the install hook is triggered. The snap_channel option will have no effect.

src/charm.py

@@ -95,11 +95,7 @@ def _write_cloud_config(self, data: dict[str, str]) -> None:
         OS_CLIENT_CONFIG.parent.mkdir(parents=True, exist_ok=True)
         OS_CLIENT_CONFIG_CACERT.write_text(self.config["ssl_ca"])
 
-        auth_url = "{protocol}://{hostname}:{port}/v3".format(
-            protocol=data["service_protocol"],
-            hostname=data["service_hostname"],
-            port=data["service_port"],
-        )
+        auth_url = f"{data['service_protocol']}://data['service_hostname']:{data['service_port']}/v3"
         contents = {
             "clouds": {
                 CLOUD_NAME: {
@@ -147,7 +143,7 @@ def get_resource(self) -> Optional[str]:
             logger.debug("cannot fetch charm resource")
             return None
 
-        if not os.path.getsize(snap_path) > 0:
+        if not os.path.getsize(snap_path):
             logger.debug("resource is an empty file")
             return None