Fix pep8 error (#169)

* Fix pep8 error

The following error is found by pep8.

```
./pifpaf/__main__.py:18:1: F401 'operator' imported but unused
import operator
```

* Always build CI image locally

It seems there is a problem with the repository maintained under
the pifpaf GitHub account. This is a short-term workaround and drops
dependency on the registry and makes the image always built during
CI run.

* Fix AttributeError

This fixes the AttributeError caused by recent version of packaging
library.

* Replace os.getlogin

... according to the recommendation in the python documentation.

.github/workflows/pifpaf.yaml

@@ -21,20 +21,6 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - run: sudo chown -R 1000:1000 $GITHUB_WORKSPACE
-      - uses: dorny/paths-filter@v2
-        id: changes
-        with:
-          filters: |
-            ci_image:
-                - 'Dockerfile'
-      - uses: docker/login-action@v2
-        with:
-          registry: ghcr.io
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
-        if: steps.changes.outputs.ci_image == 'false'
-      - run: docker pull ghcr.io/pifpaf/ci:latest
-        if: steps.changes.outputs.ci_image == 'false'
       - uses: docker/build-push-action@v2
         with:
           context: .
@@ -45,6 +31,5 @@ jobs:
             KAFKA_VERSION=${{ env.KAFKA_VERSION }}
             ETCD_VERSION=${{ env.ETCD_VERSION }}
           tags: ghcr.io/pifpaf/ci:latest
-        if: steps.changes.outputs.ci_image == 'true'
       - name: Run tox
         run: docker run --rm -v ${{ github.workspace }}:/home/pifpaf/pifpaf ghcr.io/pifpaf/ci:latest tox -e ${{ matrix.env }}

pifpaf/__main__.py

@@ -15,7 +15,6 @@
 
 import importlib.metadata
 import logging
-import operator
 import os
 import signal
 import sys

pifpaf/drivers/ceph.py

@@ -14,7 +14,7 @@
 import os
 import uuid
 
-import packaging
+import packaging.version
 
 from pifpaf import drivers
 

pifpaf/drivers/mysql.py

@@ -10,6 +10,7 @@
 # implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import getpass
 import logging
 import os
 
@@ -27,7 +28,7 @@ def _setUp(self):
         os.mkdir(datadir)
         os.mkdir(tempdir)
 
-        mysql_user_to_use = os.getlogin()
+        mysql_user_to_use = getpass.getuser()
 
         c, _ = self._exec(["mysqld",
                            "--no-defaults",