Misc fixes - See desc

* Remove unnecessary uses of _list_from_options_callback
* Fix download tests - Bug from 6e84b21559
* Rename ExecAfterDownloadPP to ExecPP and refactor its tests
* Ensure _write_ytdl_file closes file handle on error - Potential fix for #517

yt_dlp/postprocessor/__init__.py

@@ -19,7 +19,7 @@ from .ffmpeg import (
     FFmpegVideoRemuxerPP,
 )
 from .xattrpp import XAttrMetadataPP
-from .execafterdownload import ExecAfterDownloadPP
+from .exec import ExecPP, ExecAfterDownloadPP
 from .metadataparser import (
     MetadataFromFieldPP,
     MetadataFromTitlePP,
@@ -36,6 +36,7 @@ def get_postprocessor(key):
 __all__ = [
     'FFmpegPostProcessor',
     'EmbedThumbnailPP',
+    'ExecPP',
     'ExecAfterDownloadPP',
     'FFmpegEmbedSubtitlePP',
     'FFmpegExtractAudioPP',

yt_dlp/postprocessor/exec.py

@@ -11,16 +11,12 @@ from ..utils import (
 )
 
 
-class ExecAfterDownloadPP(PostProcessor):
+class ExecPP(PostProcessor):
 
     def __init__(self, downloader, exec_cmd):
-        super(ExecAfterDownloadPP, self).__init__(downloader)
+        PostProcessor.__init__(self, downloader)
         self.exec_cmd = variadic(exec_cmd)
 
-    @classmethod
-    def pp_key(cls):
-        return 'Exec'
-
     def parse_cmd(self, cmd, info):
         tmpl, tmpl_dict = self._downloader.prepare_outtmpl(cmd, info)
         if tmpl_dict:  # if there are no replacements, tmpl_dict = {}
@@ -40,3 +36,7 @@ class ExecAfterDownloadPP(PostProcessor):
             if retCode != 0:
                 raise PostProcessingError('Command returned error code %d' % retCode)
         return [], info
+
+
+class ExecAfterDownloadPP(ExecPP):  # for backward compatibility
+    pass