__ridx__ is an _undefined name_ in this context but __self.ridx__ is used three other times in this method and nine times in this class.  Undefined names may raise [NameError](https://docs.python.org/3/library/exceptions.html#NameError) at runtime.

flake8 testing of https://github.com/opencv/opencv

$ __flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics__
```
./modules/ts/misc/table_formatter.py:50:23: F821 undefined name 'ridx'
            self.rows[ridx + 1].props = properties
                      ^
```

* FIX INF_ENGINE RELU ERROR

* set slope to variable

* tab in indentwq

modules\dnn\src\layers\prior_box_layer.cpp(208): warning C4834: discarding return value of function with 'nodiscard' attribute

* Resolves 6125

* Fix test code

* Delete unnecessary code

to avoid accessing of 'p[-1]' (static code analysers dislike this)

Arm: fix the test failure of OCL_Imgproc/CLAHETest.Accuracy on ODROID-XU4 (#11409)

* fix the test failure of OCL_Imgproc/CLAHETest.Accuracy on ODROID-XU4
  * avoid the race condition in the reduce

* imgproc(ocl): simplify CLAHE code

* remove unused class

OpenCV 3.4.1 for Intel Computer Vision SDK

for cv::Mat with type=16UC3 and width < 16

std::exception_ptr requires enabled C++11 mode

- remove duplicates
- restore "always on" missing entries
- fix FP16 detection on MSVC

for cv::Mat with width < 16