Refactor sqlerror tween to add support for pyramid_retry

hopefully this doesn't break anything else..

setup.py

@@ -64,13 +64,6 @@ requires = [
     #
     # package                           # low                   high
 
-    # TODO: Pyramid 1.9 looks like it breaks us..? playing it safe for now..
-    'pyramid<1.9',                      # 1.3b2                 1.8.3
-
-    # apparently 2.0 removes the retry support, in which case we then need
-    # pyramid_retry .. but that requires pyramid 1.9 ...
-    'pyramid_tm<2.0',                   # 0.3                   1.1.1
-
     # TODO: why do we need to cap this?  breaks tailbone.db zope stuff somehow
     'zope.sqlalchemy<1.0',              # 0.7                   0.7.7
 
@@ -82,10 +75,12 @@ requires = [
     'paginate',                         # 0.5.6
     'paginate_sqlalchemy',              # 0.2.0
     'passlib',                          # 1.7.1
+    'pyramid',                          # 1.3b2
     'pyramid_beaker>=0.6',              #                       0.6.1
     'pyramid_deform',                   # 0.2
     'pyramid_exclog',                   # 0.6
     'pyramid_mako',                     # 1.0.2
+    'pyramid_tm',                       # 0.3
     'rattail[db,bouncer]',              # 0.5.0
     'six',                              # 1.10.0
     'transaction',                      # 1.2.0

tailbone/tweens.py

@@ -29,32 +29,46 @@ from __future__ import unicode_literals, absolute_import
 import six
 from sqlalchemy.exc import OperationalError
 
-from transaction.interfaces import TransientError
-
 
 def sqlerror_tween_factory(handler, registry):
     """
     Produces a tween which will convert ``sqlalchemy.exc.OperationalError``
-    instances (caused by database server restart) into a retryable
-    ``transaction.interfaces.TransientError`` instance, so that a second
-    attempt may be made to connect to the database before really giving up.
+    instances (caused by database server restart) into a retryable error
+    instance, so that a second attempt may be made to connect to the database
+    before really giving up.
 
     .. note::
        This tween alone is not enough to cause the transaction to be retried;
        it only marks the error as being *retryable*.  If you wish more than one
-       attempt to be made, you must define the ``tm.attempts`` setting within
-       your Pyramid app configuration.  For more info see `Retrying`_.
+       attempt to be made, you must define the ``retry.attempts`` (or
+       ``tm.attempts`` if running pyramid<1.9) setting within your Pyramid app
+       configuration.  For more info see `Retrying`_.
 
        .. _Retrying: http://docs.pylonsproject.org/projects/pyramid_tm/en/latest/#retrying
     """
 
     def sqlerror_tween(request):
+        try:
+            from pyramid_retry import mark_error_retryable
+        except ImportError:
+            mark_error_retryable = None
+            from transaction.interfaces import TransientError
+
         try:
             response = handler(request)
         except OperationalError as error:
+
+            # if connection is invalid, allow retry
             if error.connection_invalidated:
+                if mark_error_retryable:
+                    mark_error_retryable(error)
+                    raise error
+                else:
                     raise TransientError(six.text_type(error))
+
+            # if connection was *not* invalid, raise original error
             raise
+
         return response
 
     return sqlerror_tween