make 'path' and 'keywords' available in logging messages

Wrap all loggers used by job, extractor, downloader, and postprocessor
objects into a (custom) LoggerAdapter that provides access to the
underlying job, extractor, pathfmt, and kwdict objects and their
properties.

__init__() signatures for all downloader and postprocessor classes have
been changed to take the current Job object as their first argument,
instead of the current extractor or pathfmt.

(#574, #575)

test/test_postprocessor.py

@@ -12,12 +12,14 @@ import sys
 import unittest
 from unittest.mock import Mock, mock_open, patch
 
+import logging
 import zipfile
 import tempfile
 from datetime import datetime, timezone as tz
 
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-from gallery_dl import postprocessor, extractor, util, config  # noqa E402
+from gallery_dl import extractor, output, util  # noqa E402
+from gallery_dl import postprocessor, util, config  # noqa E402
 from gallery_dl.postprocessor.common import PostProcessor  # noqa E402
 
 
@@ -25,6 +27,15 @@ class MockPostprocessorModule(Mock):
     __postprocessor__ = "mock"
 
 
+class FakeJob():
+
+    def __init__(self):
+        self.extractor = extractor.find("test:")
+        self.pathfmt = util.PathFormat(self.extractor)
+        self.out = output.NullOutput()
+        self.get_logger = logging.getLogger
+
+
 class TestPostprocessorModule(unittest.TestCase):
 
     def setUp(self):
@@ -58,9 +69,9 @@ class BasePostprocessorTest(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
-        cls.extractor = extractor.find("test:")
         cls.dir = tempfile.TemporaryDirectory()
         config.set((), "base-directory", cls.dir.name)
+        cls.job = FakeJob()
 
     @classmethod
     def tearDownClass(cls):
@@ -74,12 +85,12 @@ class BasePostprocessorTest(unittest.TestCase):
         if data is not None:
             kwdict.update(data)
 
-        self.pathfmt = util.PathFormat(self.extractor)
+        self.pathfmt = self.job.pathfmt
         self.pathfmt.set_directory(kwdict)
         self.pathfmt.set_filename(kwdict)
 
         pp = postprocessor.find(self.__class__.__name__[:-4].lower())
-        return pp(self.pathfmt, options)
+        return pp(self.job, options)
 
 
 class ClassifyTest(BasePostprocessorTest):