AC: Move the test requirement list to a file

The "setup.py test" command is deprecated (see
pypa/setuptools#1878). I'd like to transition
CI to running pytest directly, but for that, I need an easy way to install
test dependencies. This provides such a way.

Author: Roman Donchenko

tools/accuracy_checker/requirements-test.in

@@ -0,0 +1,2 @@
+pytest==4.0.0
+pytest-mock==1.10.4

tools/accuracy_checker/setup.py

@@ -63,8 +63,6 @@ def find_version(*path):
 except ImportError:
     requirements.append('opencv-python')
 
-tests_requirements = ['pytest==4.0.0', 'pytest-mock==1.10.4']
-
 setup(
     name="accuracy_checker",
     description="Deep Learning Accuracy validation framework",
@@ -79,6 +77,6 @@ def find_version(*path):
     zip_safe=False,
     python_requires='>=3.5',
     install_requires=requirements,
-    tests_require=tests_requirements,
+    tests_require=[read("requirements-test.in")],
     cmdclass={'test': PyTest}
 )