diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 91dca89..fcb8ab4 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -28,13 +28,10 @@ jobs:
           sudo apt-get install -y tree make wget curl cloc graphviz
           dot -V
           python -m pip install --upgrade pip
-          pip install --upgrade flake8 setuptools wheel twine
-          if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
-          if [ -f requirements-test.txt ]; then pip install -r requirements-test.txt; fi
+          pip install --upgrade setuptools wheel twine
+          pip install -r requirements.txt
+          pip install -r requirements-test.txt
+          pip install -r requirements-lint.txt
       - name: Basic lint with flake8
         run: |
-          flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
-          flake8 ./plantumlcli --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
-      - name: Lint with flake8
-        run: |
-          flake8 ./plantumlcli
\ No newline at end of file
+          make flake
diff --git a/.github/workflows/sync.yml b/.github/workflows/sync.yml
index f884f3f..7b0f7ba 100644
--- a/.github/workflows/sync.yml
+++ b/.github/workflows/sync.yml
@@ -2,8 +2,6 @@ name: Repository Sync
 
 on:
   push:
-  schedule:
-    - cron: '0 1 * * *'
 
 jobs:
   sync:
diff --git a/Makefile b/Makefile
index 7b88336..e1ede51 100644
--- a/Makefile
+++ b/Makefile
@@ -46,3 +46,9 @@ docs:
 	$(MAKE) -C "${DOC_DIR}" build
 pdocs:
 	$(MAKE) -C "${DOC_DIR}" prod
+
+flake:
+	flake8 ./plantumlcli --count --select=E9,F63,F7,F82 --show-source --statistics
+	flake8 ./plantumlcli --count --exit-zero \
+		--max-complexity=10 --max-line-length=127 --statistics \
+		--per-file-ignores="__init__.py:F401"
diff --git a/plantumlcli/entry/cli.py b/plantumlcli/entry/cli.py
index 940109a..b8a3074 100644
--- a/plantumlcli/entry/cli.py
+++ b/plantumlcli/entry/cli.py
@@ -72,7 +72,8 @@ def validate_concurrency(ctx: Context, param: Option, value: int):
 @click.option('-p', '--plantuml', envvar=PLANTUML_JAR_ENV, type=str, default=None,
               help=f'Path of plantuml jar file (will load from ${{{PLANTUML_JAR_ENV}}} when not given).')
 @click.option('-r', '--remote-host', envvar=PLANTUML_HOST_ENV, type=str, default=OFFICIAL_PLANTUML_HOST,
-              help=f'Remote host of the online plantuml editor (will load from ${{{PLANTUML_HOST_ENV}}} when not given).',
+              help=f'Remote host of the online plantuml editor '
+                   f'(will load from ${{{PLANTUML_HOST_ENV}}} when not given).',
               show_default=True)
 @click.option('-L', '--use-local', is_flag=True, help='Use local plantuml only.')
 @click.option('-R', '--use-remote', is_flag=True, help='Use remote plantuml only.')
@@ -80,7 +81,7 @@ def validate_concurrency(ctx: Context, param: Option, value: int):
 @click.option('-u', '--url', is_flag=True, help='Print url of remote plantuml resource (ignore -L and -R).')
 @click.option('--homepage-url', is_flag=True, help='Print url of remote plantuml editor (ignore -L, -R and -u).')
 @click.option('-t', '--type', 'resource_type', default=PlantumlResourceType.PNG.name,
-              type=click.Choice(PlantumlResourceType.__members__.keys(), case_sensitive=False),
+              type=click.Choice(list(PlantumlResourceType.__members__.keys()), case_sensitive=False),
               help='Type of plantuml resource.', show_default=True)
 @click.option('-T', '--text', is_flag=True, help='Display text uml graph by stdout (ignore -t).')
 @click.option('-o', '--output', type=str, multiple=True,
diff --git a/plantumlcli/entry/general.py b/plantumlcli/entry/general.py
index 49a093e..a00c5d2 100644
--- a/plantumlcli/entry/general.py
+++ b/plantumlcli/entry/general.py
@@ -57,7 +57,7 @@ def print_check_info(check_type: PlantumlCheckType,
         pass
 
 
-def print_text_graph(plantuml: Plantuml, sources: Tuple[str], concurrency: int):
+def print_text_graph(plantuml: Plantuml, sources: Tuple[str], concurrency: int):  # noqa
     """
     Print text graph of source codes
     :param plantuml: plantuml object
diff --git a/plantumlcli/utils/concurrent.py b/plantumlcli/utils/concurrent.py
index dbc8080..a804224 100644
--- a/plantumlcli/utils/concurrent.py
+++ b/plantumlcli/utils/concurrent.py
@@ -12,10 +12,8 @@ def _default_final_error_process(errors: List[Tuple[int, _Ti, Exception]]):
     raise err
 
 
-def linear_process(items: Iterable[_Ti],
-                   process: Callable[[int, _Ti], _Tr],
-                   post_process: Callable[[int, _Ti, _Tr], None],
-                   concurrency: int = None,
+def linear_process(items: Iterable[_Ti], process: Callable[[int, _Ti], _Tr],  # noqa
+                   post_process: Callable[[int, _Ti, _Tr], None], concurrency: int = None,
                    skip_once_error: bool = True,
                    final_error_process: Optional[Callable[[List[Tuple[int, _Ti, Exception]]], None]] = None):
     concurrency = concurrency or cpu_count()