Drop spurious setup requirements

Since setuptools 46.4.0 (May 2020), `attr:` are statically extracted
using the `ast` module if possible:

	pypa/setuptools#1753

Author: nbraud

pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
 # Minimum requirements for the build system to execute.
-requires = ["setuptools", "wheel"] # PEP 508 specifications.
+requires = ["setuptools>=46.4.0", "wheel"] # PEP 508 specifications.
 
 # Actually tell PEP517 tools to call setuptools
 build-backend = "setuptools.build_meta"

setup.py

@@ -15,8 +15,7 @@ def requirements(section=None):
 
 # See setup.cfg for the actual configuration.
 setup(
-    # setup needs to be able to import the library, for attr: to work
-    setup_requires=requirements() + ['pytest-runner'],
+    setup_requires=['pytest-runner'],
     install_requires=requirements(),
     tests_require=requirements('tests'),
 )