This Commit fixes failing system tests in ISIS powder polaris.

re: #28415

this commit adds system tests covering the new rebin options in the polaris create total scattering script.

re: #28415

Accidentally removed inheritance of systemtesting.MantidSystemTest when
removing with_metaclass and add_metaclass. Put them back.

Removes all of the from __future__ imports that open and close the
brackets on the same line. This is most of them.

Add feature where an externally generated attenuation profile can be loaded into
the material definition from a .DAT text file. This will override the normal
exp(-alpha*thickness) calculation of the attenuation. The new feature was requested
as part of the absorption calculation for the Pearl instrument where some parts
of the environment are crystalline

Found the lookup\interpolation on the loaded profile was slowing down the absorption
Monte Carlo calculation.
So improved performance of Kernel::Interpolation. Changed it to use vector of pairs
instead of two separate vectors to reduce amount of navigation around vectors

Considered adding feature into AttenuationProfile where I add any interpolated points
into the override attenuation profile to prevent interpolation next iteration of
Monte Carlo simulation. However wasn't convinced this was going to be thread-safe
during the parallel part of the absorption calculation - may revisit this. While doing
this investigation I fixed the following issues with the function Interpolation::AddPoint:

a) it doesn't add the same point twice
b) it reuses the lower_bound function rather than stepping through the vector sequentially

I removed the exception from findIndexOfNextLargerValue because the end()
iterator is a valid result if the x value supplied equals the last x value
already in the vector. Could have left check in for begin() but didn't seem
much point

Finally - the interpolation outside the range is not v good. The data at the extremes
is noisy so we end up extrapolating based on random gradient in extreme 2 points. Need
to either fit or use more points to determine gradient

Also updated class_maker.py

Attempts to flush out the cause for the failing nightly clean build on
Windows. This is periodically failing on both the release / master clean
builds without any reason why.

Fixes all flake8 3.7.9 warnings as part of the Python 2->3 transition.

This commit replaces all header guards in testing with #pragma once.

subprocess.communicate returns a bytes object but File.write requires a str object

The stdDev function that was deleted in this branch often returns different values  than the 'correct' value which is sqrt(eigenvalue)  - which is now used. Typically the difference is  <0.5%, however occasionally the stdDev function returned a std deviation that is unrealistically small (by two orders of magnitude), this behavior is not as yet understood, but since the function is no longer used it is appropriate to change the test values.

This commit updates the reference files for tests where the transmission
workspace is output from ReflectometryReductionOne. The refactored code
in this PR has introduced a fix in this algorithm to output the
transmission workspace after it has been rebinned to detectors.
Previously it was output before the rebin step, hence the minor
differences in the output. Note however that the final results of the
reduction (IvsQ workspaces) are unchanged.

This commit also moves the code to set the output workspace to the
bottom of the function that does the transmission correction, to help
avoid a similar problem happening again.

Re #27633

When assigning to a list of outputs when calling the algorithm in
python, the outputs must be specified in the order they are declared,
even if they are optional outputs like IvsLam. This means that if we
want to specify the transmission workspace output we must first specify
IvsLam even if debug is false. Some of the algorithms always output
IvsLam if the name was given whereas others did not. They now always
output it if the name is given.

Note that this means you may now get an error if you don't supply enough
arguments whereas previously it was ok. It is ok if you just specify the
IvsQ output(s) but beyond that we do not know whether the output should
be IvsLam or the transmission, so we require all of them, hence the
error. This is better than it assigning an unexpected output so I think
is ok, and is the only way I can think to do this.

Re #27633

Signed-off-by: Jose Borreguero <borreguero@gmail.com>

System tests for Abins are modified to calculate up to second-order
excitations only (as third and fourth-order are currently disabled.)

In addition, the test data for two other tests needs updating;
BezeneBinWidthCASTEP and TolueneScale have small changes in the
results. This is associated with a more conservative criterion for
discarding small values compared to the previous system; results
similar to the previous setup can be obtained by modifying the
threshold used in
SPowderSemiEmpiricalCalculator._calculate_s_over_threshold

Signed-off-by: Jose Borreguero <borreguero@gmail.com>