- ensure we escape out percent signs when a CompiledSQL or RegexSQL
has percent signs in the SQL or in the parameter repr

- to support combinations, print out complete test name in skip
messages, py.test environment gives us a way to do this

Change-Id: Ia9e62f7c1026c1465986144c5757e35fc164a2b8

Like py.test we need to be able to mark certain combination
elements with exclusion rules.   Add additional logic
to pytestlplugin and exclusions so that the exclusion decorators
can be added to the combination tuples, where they will be applied
to the decorated function along with a qualifier that the test
arguments need to match what's given.

Change-Id: I15d2839954d77a252bab5aaf6e3fd9f388c99dd5

Dialect tests tend to have a lot of lists of types,
SQL constructs etc, convert as many of these to @combinations
as possible.

This is exposing that we don't have per-combination
exclusion rules set up which is making things a little bit
cumbersome.

Also set up a fixture that does metadata + DDL.

Change-Id: Ief820e48c9202982b0b1e181b87862490cd7b0c3

Add factilities to implement pytest.mark.parametrize and
pytest.fixtures patterns, which largely resemble things we are
already doing.

Ensure a facade is used, so that the test suite remains independent
of py.test, but also tailors the functions to the more limited
scope in which we are using them.

Additionally, create a class-based version that works from the
same facade.

Several old polymorphic tests as well as two of the sql test
are refactored to use the new features.

Change-Id: I6ef8af1dafff92534313016944d447f9439856cf
References: #4896

this seems to be the best place to put this as it is guaranteed
before the module is imported.   this is for the benefit of
3rd party dialects that also would have this in their conftest.py,
so that they don't have to do the "bootstrap" loading hack.

Change-Id: Ieae5324240e04a7919df46f4fca03f8db7a2af81

I use the nfl sort a lot to see what calling changes are happening
between two versions in order to identify the offending code, so
add it as a command line option.

Change-Id: Ia1ab6dd98012a78298b325bb5c7c050fa9b767c2

support that we have pytest-xdist arguments now,
as well as allow force-write to reset the list of callcounts which
seem to accumulate commas for some reason

Change-Id: I54dd164c21ffbb9139937d5c3ffb1df7e9598594

Since our various eq_(), ne_() etc. functions use assert, pytest
can rewrite this module using its enhanced string reporting.
very helpful for comparing SQL strings

Change-Id: Ia71328401fd7965bcb14eb1ccea0dc48a8f2c3ea

The memusage tests are extremely time and memory intensive,
and when CI runs against MySQL or Postgresql there are many
database/driver combinations for which the "backend" tests
repeatedly run; as these tests are more oriented towards
basic dialect interaction, add a new "sparse" backend option
that will run the tests only once per base dialect.

Change-Id: I312aa0332d7ec1ff4e2faa15f6b189d6f0f68393

This is a very useful assertion which prevents unused variables
from being set up allows code to be more readable and sometimes
even more efficient.  test suites seem to be where the most
problems are and there do not seem to be documentation examples
that are using this, or at least the linter is not taking effect
within rst blocks.

Change-Id: I2b3341d8dd14da34879d8425838e66a4b9f8e27d