Applied an explicit "cause" to most if not all internally raised exceptions
that are raised from within an internal exception catch, to avoid
misleading stacktraces that suggest an error within the handling of an
exception.  While it would be preferable to suppress the internally caught
exception in the way that the ``__suppress_context__`` attribute would,
there does not as yet seem to be a way to do this without suppressing an
enclosing user constructed context, so for now it exposes the internally
caught exception as the cause so that full information about the context
of the error is maintained.

Fixes: #4849
Change-Id: I55a86b29023675d9e5e49bc7edc5a2dc0bcd4751

The technique arrived at for doing exclusions inside of combinations
relies upon comparing all the arguments in a particular combination
to some set of combinations that were gathered as having
"exclusions".   This logic is actually broken for the
case where the @testing.combinations has an "id", but if we fix
that, we still have the issue of all the arguments being
compared, which is complicated and also doesn't work for the
case of a py2/py3 incompatibility like a timezone that has
fractional minutes or seconds in it.   It's also not clear
if a @testing.combinations that uses lambdas will work either
(maybe it does though because lambdax == lambdax compares...).

anyway, this patch reworks it so that we hit this on the decorator
side instead, where we add our own decorator and go through
the extra effort to create a decorator that accepts an extra
argument of "exclusions" which we can then check in a way that
is local to the whole pytest @combinations thing in the first place.
The only difficulty is that pytest is very sneaky about looking
at the test function so we need to make sure __wrapped__ isn't
set when doing this.

Change-Id: Ic57aae15b378e0f4ed009e4e82ae7ba73fb6dfc5

In Ia63a510f9c1d08b055eef62cf047f1f427f0450c we introduced
"lambda combinations" which use a bit of function closure inspection
in order to allow for testing combinations that make use of symbols that
come from test fixtures, or from the test itself.

Two problems.  One is that we can't use F821 flake8 rule without either
adding lots of noqas, skipping the file, or adding arguments to the
lambdas themselves that are then populated, which makes for a very
verbose system.  The other is that the system is already verbose
with all those lambdas and the magic in use is a non-explicit kind,
hence F821 reminds us that if we can improve upon this, we should.

So let's improve upon it by making it so that the "lambda" is just
once and up front for the whole thing, and let it accept the arguments
directly.   This still requires magic, because these test cases need
to resolve at test collection time, not test runtime.  But we will
instead substitute a namespace up front that can be coerced into
its desired form within the tests.

Additionally, there's a little bit of py2k compatible type annotations
present; f821 is checking these, so we have to add those imports
also using the TYPE_CHECKING boolean so they don't take place in
py2k.

Change-Id: Idb7e7a0c8af86d9ab133f548511306ef68cdba14

Change-Id: I08440dc25e40ea1ccea1778f6ee9e28a00808235

- 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

The fails_on decorator was not being interpreted
correctly when multiple were present.

Remove obsolete fails_on from test_types that no longer
take place for MySQL, Oracle.

Ensure test_types tests are using __backend__

mark currently failing Oracle interval tests

Change-Id: If8db0c02b31a8008fd1673c2380f1f974c3806a6

Fixes: #4850

<!-- Provide a general summary of your proposed changes in the Title field above -->

### Description
<!-- Describe your changes in detail -->

Removes usage of `util.callable`.

### Checklist
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This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [x] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #4851
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4851
Pull-request-sha: a0ccdff2cb74f5e944d8baccc269c382b591c8e2

Change-Id: I79918f44becbc5dbefdc7ff65128695c1cabed1d

Replace inspect_getargspec with inspect_getfullargspec
including a compatibility fallback for Py2k and use
getfullargspec fully.

Change-Id: I92bce0aafc37ce1a360b4f61b75f5892d0911c7e

Change-Id: I6a71f4924d046cf306961c58dffccf21e9c03911