libpq's PQescapeString will use the same encoding it has seen before in
a connection (static_client_encoding).
So I think I'll leave this feature here for people who know what is
doing, but won't really document it as a feature: it can't really work
in a generic way (unless adding some disgusting hack like creating a
fake connection with the encoding we want to call PQescapeStringConn
instead of PQescapeString).
Dropped encoding parameter in the constructor: it is used
nowhere and not documented. Use directly the connection
encoding if available, else the previous latin1 fallback.
Dropped cyclic import from modules to tests: they were only working
because a second copy of the package was found in the project dir.
Use relative import so that 2to3 can do a good conversion.
* tests/*.py: use the DSN constructed in tests/__init__.py.
* tests/__init__.py: allow setting the host, port and user for the
DSN used by the tests through the environment.
requiring it.
Added a connection flag to store whether E''-style quoting is required: this
avoids repeated PQparameterStatus() calls.
Added a test case to verify correct behavior on strings, unicode and binary
data. Tested with PG versions from 7.4 to 8.3b2, with any server
'standard_conforming_strings' setting and with 'PSYCOPG_OWN_QUOTING' too.
