replaced script with entry point in setup.py

The `setup.py` specified previously a script which caused problems when
running pyicontract-lint on Windows (*e.g.*, Windows could not find the
interpreter since the shebang is ignored). This change removes the
script and specifies an entry point in `setup.py` so that the executable
is correctly created on Windows upon installation.

See also:
https://setuptools.readthedocs.io/en/latest/setuptools.html#automatic-script-creation

icontract_lint/main.py

@@ -60,7 +60,7 @@ def _main(args: Args, stream: TextIO) -> int:
     return 0
 
 
-def main() -> None:
+def main() -> int:
     """Wrap the main routine so that it can be tested."""
     args = parse_args(sys_argv=sys.argv)
-    sys.exit(_main(args=args, stream=sys.stdout))
+    return _main(args=args, stream=sys.stdout)

precommit.py

@@ -28,26 +28,26 @@ def main() -> int:
     if overwrite:
         subprocess.check_call(
             [
-                "yapf", "--in-place", "--style=style.yapf", "--recursive", "tests", "icontract_lint",
-                "bin/pyicontract-lint", "setup.py", "precommit.py"
+                "yapf", "--in-place", "--style=style.yapf", "--recursive", "tests", "icontract_lint", "setup.py",
+                "precommit.py"
             ],
             cwd=repo_root.as_posix())
     else:
         subprocess.check_call(
             [
-                "yapf", "--diff", "--style=style.yapf", "--recursive", "tests", "icontract_lint",
-                "bin/pyicontract-lint", "setup.py", "precommit.py"
+                "yapf", "--diff", "--style=style.yapf", "--recursive", "tests", "icontract_lint", "setup.py",
+                "precommit.py"
             ],
             cwd=repo_root.as_posix())
 
     print("Mypy'ing...")
-    subprocess.check_call(["mypy", "icontract_lint", "bin/pyicontract-lint", "tests"], cwd=repo_root.as_posix())
+    subprocess.check_call(["mypy", "icontract_lint", "tests"], cwd=repo_root.as_posix())
 
     print("Pylint'ing...")
     subprocess.check_call(["pylint", "--rcfile=pylint.rc", "tests", "icontract_lint"], cwd=repo_root.as_posix())
 
     print("Pydocstyle'ing...")
-    subprocess.check_call(["pydocstyle", "icontract_lint", "bin/pyicontract-lint"], cwd=repo_root.as_posix())
+    subprocess.check_call(["pydocstyle", "icontract_lint"], cwd=repo_root.as_posix())
 
     print("Testing...")
     env = os.environ.copy()

setup.py

@@ -31,7 +31,9 @@
         'Intended Audience :: Developers',
         'License :: OSI Approved :: MIT License',
         'Programming Language :: Python :: 3.5',
-        'Programming Language :: Python :: 3.6'
+        'Programming Language :: Python :: 3.6',
+        'Operating System :: Microsoft :: Windows',
+        'Operating System :: POSIX'
         # yapf: enable
     ],
     license='License :: OSI Approved :: MIT License',
@@ -42,7 +44,7 @@
         'dev': [
             # yapf: disable
             'mypy==0.620',
-            'pylint==2.1.1',
+            'pylint==2.3.0',
             'yapf==0.20.2',
             'tox>=3.0.0',
             'pydocstyle>=2.1.1,<3',
@@ -51,7 +53,7 @@
             # yapf: enable
         ],
     },
-    scripts=['bin/pyicontract-lint'],
+    entry_points={"console_scripts": ["pyicontract-lint = icontract_lint.main:main"]},
     py_modules=['icontract_lint', 'pyicontract_lint_meta'],
     include_package_data=True,
     package_data={