synchrotron: Print nicer message if lock can not be acquired

Resolves: #25

src/laniakea/utils/__init__.py

@@ -6,6 +6,7 @@
 
 from laniakea.utils.json import json_compact_dump
 from laniakea.utils.misc import (
+    LockError,
     cd,
     listify,
     stringify,
@@ -46,6 +47,7 @@
     'safe_run',
     'run_forwarded',
     'safe_run_forwarded',
+    'LockError',
     'cd',
     'listify',
     'stringify',

src/laniakea/utils/misc.py

@@ -123,6 +123,10 @@ def datetime_to_rfc2822_string(dt: datetime):
     return utils.format_datetime(dt)
 
 
+class LockError(Exception):
+    """An error happened while acquiring a file lock."""
+
+
 class ProcessFileLock:
     """
     Simple wy to prevent multiple processes from executing the same code via a file lock.
@@ -169,7 +173,7 @@ def acquire(self, raise_error=True) -> bool:
             self._lock_file_fd = -1
             os.close(fd)
             if raise_error:
-                raise Exception(
+                raise LockError(
                     'Unable to acquire lock "{}": Lock held by other instance or thread!'.format(self.lock_filename)
                 )
             return False

src/spears/excuses.py

@@ -91,7 +91,7 @@ def get_excuses(self) -> Dict[str, SpearsExcuse]:
             'Additional info:',
             ' days old (needed ',
         )
-        debian_buildd_link_re = r'<a href="https://buildd\.debian\.org/status/logs\.php\?arch=[^&]+&pkg=[^&]+&ver=[^"]+" target="_blank">([^<]+)</a>'
+        debian_buildd_link_re = r'<a href="https://buildd\.debian\.org/status/logs\.php\?arch=[^&]+&pkg=[^&]+&ver=[^"]+" target="_blank">([^<]+)</a>'  # noqa: E501
 
         # get log data
         loginfo = self._process_log_data()

src/synchrotron/cli.py

@@ -9,6 +9,7 @@
 from argparse import ArgumentParser
 
 from laniakea.db import SynchrotronConfig, session_scope
+from laniakea.utils import LockError
 from laniakea.logging import log
 
 from .syncengine import SyncEngine, SyncSetupError
@@ -26,12 +27,16 @@ def command_sync(options):
     try:
         engine = SyncEngine(options.repo_name, options.dest_suite, options.src_os, options.src_suite)
     except SyncSetupError as e:
-        print('Unable to setup synchronization:', str(e))
+        print('Unable to setup synchronization:', str(e), file=sys.stderr)
         sys.exit(1)
 
-    ret = engine.sync_packages(options.component, options.packages, options.force)
-    if not ret:
-        sys.exit(2)
+    try:
+        ret = engine.sync_packages(options.component, options.packages, options.force)
+        if not ret:
+            sys.exit(2)
+    except LockError as e:
+        print('Locking failed:', str(e), file=sys.stderr)
+        sys.exit(4)
 
 
 def command_autosync(options):
@@ -65,12 +70,16 @@ def command_autosync(options):
                     autosync.source.suite_name,
                 )
             except SyncSetupError as e:
-                print('Unable to setup synchronization:', str(e))
+                print('Unable to setup synchronization:', str(e), file=sys.stderr)
                 sys.exit(1)
 
-            ret = engine.autosync(autosync.auto_cruft_remove)
-            if not ret:
-                sys.exit(2)
+            try:
+                ret = engine.autosync(autosync.auto_cruft_remove)
+                if not ret:
+                    sys.exit(2)
+            except LockError as e:
+                print('Locking failed:', str(e), file=sys.stderr)
+                sys.exit(4)
 
             # commit pending changes
             session.commit()