Failing AccurateRipResponse tests

[JoeLametta]

Travis CI is reporting 3 test failures which don't depend on recent changes introduced by us: we should investigate what's the cause and update the tests to fix the failures.

....WARNING:whipper.common.mbngs:Release with ID '3451f29c-9bb8-4cc5-bfcc-bd50104b94f8' (Jeff Buckley - Everybody Here Wants You) does not have a date
..............ERROR:whipper.common.accurip:no track AR CRC on non-HTOA track 1
......FERROR:whipper.common.accurip:could not save entry to /tmp/tmp9x4Fmywhipper_accurip_cache_test/c/1/2/dBAR-002-0000f21c-00027ef8-05021002.bin: "[Errno 13] Permission denied: '/tmp/tmp9x4Fmywhipper_accurip_cache_test/c'"
FERROR:whipper.common.accurip:error retrieving AccurateRip entry: 404 Not Found <Response [404]>
WARNING:whipper.common.accurip:entry not found in AccurateRip database
.F.WARNING:whipper.program.arc:ARC calculation failed: arc return code is non zero: 1
ERROR:whipper.common.accurip:could not calculate AccurateRip v1 checksum for track 1 '/does/not/exist'
WARNING:whipper.program.arc:ARC calculation failed: arc return code is non zero: 1
ERROR:whipper.common.accurip:could not calculate AccurateRip v2 checksum for track 1 '/does/not/exist'
.............................................................................
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FAIL: test_AccurateRipResponse_parses_correctly (whipper.test.test_common_accurip.TestAccurateRipResponse)
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Traceback (most recent call last):
  File "/home/travis/build/whipper-team/whipper/whipper/test/test_common_accurip.py", line 81, in test_AccurateRipResponse_parses_correctly
    self.assertEqual(responses[1].confidences[0], 4)
AssertionError: 5 != 4

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FAIL: test_can_return_entry_without_saving (whipper.test.test_common_accurip.TestAccurateRipResponse)
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Traceback (most recent call last):
  File "/home/travis/build/whipper-team/whipper/whipper/test/test_common_accurip.py", line 54, in test_can_return_entry_without_saving
    self.assertEqual(get_db_entry(self.path), self.entry)
AssertionError: Lists differ: [<whipper.common.accurip._Accu... != [<whipper.common.accurip._Accu...

First differing element 0:
<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7c3da90>
<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7e87f50>

- [<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7c3da90>,
?                                                                 ^^^^^

+ [<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7e87f50>,
?                                                                 ^^^^^

-  <whipper.common.accurip._AccurateRipResponse object at 0x7f03a7c3d250>]
?                                                                 ^^^^^

+  <whipper.common.accurip._AccurateRipResponse object at 0x7f03a7e87e90>]
?                                                                 ^^^^^


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FAIL: test_retrieves_and_saves_accuraterip_entry (whipper.test.test_common_accurip.TestAccurateRipResponse)
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Traceback (most recent call last):
  File "/home/travis/build/whipper-team/whipper/whipper/test/test_common_accurip.py", line 61, in test_retrieves_and_saves_accuraterip_entry
    self.assertEqual(get_db_entry(self.path), self.entry)
AssertionError: Lists differ: [<whipper.common.accurip._Accu... != [<whipper.common.accurip._Accu...

First differing element 0:
<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7c3d250>
<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7e87f50>

- [<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7c3d250>,
?                                                                 ^^^^

+ [<whipper.common.accurip._AccurateRipResponse object at 0x7f03a7e87f50>,
?                                                                 ^^^^

-  <whipper.common.accurip._AccurateRipResponse object at 0x7f03a7c3da90>]
?                                                                 ^^^^

+  <whipper.common.accurip._AccurateRipResponse object at 0x7f03a7e87e90>]
?                                                                 ^^^^


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