"WARNING: Writing cache to '...' failed"

[doublex]

./youtube-dl-2014.07.11.3 --verbose 'www.youtube.com/watch?v=TVDREzBijRI'
[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['--verbose', 'www.youtube.com/watch?v=TVDREzBijRI']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2014.07.11.3
[debug] Python version 2.6.6 - Linux-2.6.32-358.18.1.el6.x86_64-x86_64-with-centos-6.5-Final
[debug] Proxy map: {}
[youtube] Setting language
[youtube] TVDREzBijRI: Downloading webpage
[youtube] TVDREzBijRI: Downloading video info webpage
[youtube] TVDREzBijRI: Extracting video information
[youtube] TVDREzBijRI: Encrypted signatures detected.
[youtube] encrypted signature length 84 (40.43), itag 43, html5 player en_US-vfl0Cbn9e
[youtube] TVDREzBijRI: Downloading js player vfl0Cbn9e
WARNING: Writing cache to u'/home/login/.cache/youtube-dl/youtube-sigfuncs/js_vfl0Cbn9e_84.json' failed: Traceback (most recent call last):
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 391, in _extract_signature_function
    cache_res = res(test_string)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 449, in <lambda>
    return lambda s: initial_function([s])
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 113, in resf
    res = self.interpret_statement(stmt, local_vars)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 45, in interpret_statement
    v = self.interpret_expression(expr, local_vars, allow_recursion)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 58, in interpret_expression
    val = local_vars[m.group('in')]
KeyError: u'fo'

ERROR: Automatic signature extraction failed: Traceback (most recent call last):
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 883, in _decrypt_signature
    return func(s)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 449, in <lambda>
    return lambda s: initial_function([s])
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 113, in resf
    res = self.interpret_statement(stmt, local_vars)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 45, in interpret_statement
    v = self.interpret_expression(expr, local_vars, allow_recursion)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 58, in interpret_expression
    val = local_vars[m.group('in')]
KeyError: u'fo'
; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type  youtube-dl -U  to update.
Traceback (most recent call last):
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 883, in _decrypt_signature
    return func(s)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 449, in <lambda>
    return lambda s: initial_function([s])
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 113, in resf
    res = self.interpret_statement(stmt, local_vars)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 45, in interpret_statement
    v = self.interpret_expression(expr, local_vars, allow_recursion)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 58, in interpret_expression
    val = local_vars[m.group('in')]
KeyError: u'fo'
Traceback (most recent call last):
  File "./youtube-dl-2014.07.11.3/youtube_dl/YoutubeDL.py", line 516, in extract_info
    ie_result = ie.extract(url)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/common.py", line 168, in extract
    return self._real_extract(url)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 1249, in _real_extract
    encrypted_sig, video_id, player_url, age_gate)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 887, in _decrypt_signature
    u'Automatic signature extraction failed: ' + tb, cause=e)
ExtractorError: Automatic signature extraction failed: Traceback (most recent call last):
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 883, in _decrypt_signature
    return func(s)
  File "./youtube-dl-2014.07.11.3/youtube_dl/extractor/youtube.py", line 449, in <lambda>
    return lambda s: initial_function([s])
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 113, in resf
    res = self.interpret_statement(stmt, local_vars)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 45, in interpret_statement
    v = self.interpret_expression(expr, local_vars, allow_recursion)
  File "./youtube-dl-2014.07.11.3/youtube_dl/jsinterp.py", line 58, in interpret_expression
    val = local_vars[m.group('in')]
KeyError: u'fo'
; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type  youtube-dl -U  to update.

[TheKorn2]

Same issue here, figure another bug report can't hurt.

[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['http://www.youtube.com/watch?v=8Gv0H-vPoDc', '--verbose']
[debug] Encodings: locale UTF-8, fs UTF-8, out None, pref UTF-8
[debug] youtube-dl version 2014.07.11.3
[debug] Python version 2.7.3 - Linux-3.2.0-65-generic-x86_64-with-Ubuntu-12.04-precise
[debug] Proxy map: {}
[youtube] Setting language
[youtube] 8Gv0H-vPoDc: Downloading webpage
[youtube] 8Gv0H-vPoDc: Downloading video info webpage
[youtube] 8Gv0H-vPoDc: Extracting video information
[youtube] 8Gv0H-vPoDc: Encrypted signatures detected.
[youtube] encrypted signature length 84 (40.43), itag 22, html5 player en_US-vfl0Cbn9e
[youtube] 8Gv0H-vPoDc: Downloading js player vfl0Cbn9e
WARNING: Writing cache to u'/home/vince/.cache/youtube-dl/youtube-sigfuncs/js_vfl0Cbn9e_84.json' failed: Traceback (most recent call last):
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 391, in _extract_signature_function
cache_res = res(test_string)
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 449, in
return lambda s: initial_function([s])
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 113, in resf
res = self.interpret_statement(stmt, local_vars)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 45, in interpret_statement
v = self.interpret_expression(expr, local_vars, allow_recursion)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 58, in interpret_expression
val = local_vars[m.group('in')]
KeyError: u'fo'

ERROR: Automatic signature extraction failed: Traceback (most recent call last):
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 883, in _decrypt_signature
return func(s)
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 449, in
return lambda s: initial_function([s])
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 113, in resf
res = self.interpret_statement(stmt, local_vars)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 45, in interpret_statement
v = self.interpret_expression(expr, local_vars, allow_recursion)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 58, in interpret_expression
val = local_vars[m.group('in')]
KeyError: u'fo'
; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type youtube-dl -U to update.
Traceback (most recent call last):
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 883, in _decrypt_signature
return func(s)
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 449, in
return lambda s: initial_function([s])
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 113, in resf
res = self.interpret_statement(stmt, local_vars)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 45, in interpret_statement
v = self.interpret_expression(expr, local_vars, allow_recursion)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 58, in interpret_expression
val = local_vars[m.group('in')]
KeyError: u'fo'
Traceback (most recent call last):
File "/usr/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 516, in extract_info
ie_result = ie.extract(url)
File "/usr/bin/youtube-dl/youtube_dl/extractor/common.py", line 168, in extract
return self._real_extract(url)
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 1249, in _real_extract
encrypted_sig, video_id, player_url, age_gate)
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 887, in _decrypt_signature
u'Automatic signature extraction failed: ' + tb, cause=e)
ExtractorError: Automatic signature extraction failed: Traceback (most recent call last):
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 883, in _decrypt_signature
return func(s)
File "/usr/bin/youtube-dl/youtube_dl/extractor/youtube.py", line 449, in
return lambda s: initial_function([s])
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 113, in resf
res = self.interpret_statement(stmt, local_vars)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 45, in interpret_statement
v = self.interpret_expression(expr, local_vars, allow_recursion)
File "/usr/bin/youtube-dl/youtube_dl/jsinterp.py", line 58, in interpret_expression
val = local_vars[m.group('in')]
KeyError: u'fo'
; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type youtube-dl -U to update.

[jaimeMF]

Duplicate of #3255.