pyramid_tm broken on Python 2 with transaction 2.0

[jamadden]

Transaction 2.0 defined the transaction note, username and description to all be text (unicode on Python 2.0), but pyramid_tm passes native_ values (meaning str/bytes on Python 2). This leads directly to TypeError (prior to 2.0.3, it could lead to UnicodeError in some cases). (See zopefoundation/transaction#34 for a specific stack trace.)

I'm willing to offer a PR to address this.

[tseaver]

@jamadden ISTM we are going to need to release pyramid_tm 1.0.2, pinning the dependency to transaction < 2.0dev, and then fix the master to pin it transaction >= 2.0.

[mmerickel]

I agree with @tseaver that this will require 2 releases from 2 PRs to handle properly.

[mmerickel]

I can take care of getting 1.0.2 out tonight at least. If you wanted to submit a PR for master against transaction 2.0 and confirm that it works for you that would be greatly appreciated.

[jamadden]

Existing storages, when passed unicode under transaction < 2 (and ZODB < 5.0.?), would accept it and encode it as ASCII or UTF8. If we're willing to accept the risk of UnicodeDecodeErrors there, we could simply always pass in the unicode and work with all versions of transaction.

Alternately, we can detect the behaviour of transaction by checking hasattr(Transaction(), 'extension'). If it's false, we can send the native string. If it's true, we can simply pass through the unicode. That seems pretty easy.

if hasattr(Transaction(), 'extension'):
   def tx_string(s): return text(s)
else:
   tx_string = native_

[mmerickel]

Alternately, we can detect the behaviour of transaction by checking hasattr(Transaction(), 'extension'). If it's false, we can send the native string. If it's true, we can simply pass through the unicode. That seems pretty easy.

I don't think I like this fix. The hasattr check is unrelated to the actual issue at hand and feels unreliable down the road if transaction 3.0 drops extension then it's unclear why .note stopped working.

[jamadden]

Ok, how about simply passing in a byte string and seeing what happens?

try:
   Transaction().note(b'bytes')
except TypeError:
   def tx_string(s): return text(s)
else:
   def tx_string(s): return bytes(s) # whatever the compat function is called

[jamadden]

I should note that passing in the native string type is a bug of its own on Python 3, because of the ASCII decoding that storages will do to store the text as bytes. So there are already UnicodeErrors lurking.

[mmerickel]

Ok pyramid_tm 1.0.2 is pinned to transaction < 1.99 to avoid anyone automatically upgrading.

[mmerickel]

@jamadden Could you please comment on #50 and whether it works for you or not?