use a real python 3.5 to generate frozen reqs

requirements.d/development.txt

@@ -1,11 +1,11 @@
-setuptools !=60.6.0, !=60.7.0
-setuptools_scm
-pip
-virtualenv
-tox
-pytest
-pytest-xdist
-pytest-cov
-pytest-benchmark
-Cython
-twine
+setuptools==28.8.0
+setuptools-scm==5.0.2
+pip==20.3.4
+virtualenv==20.13.1
+tox==3.24.5
+pytest==6.1.2
+pytest-xdist==2.2.1
+pytest-cov==2.12.1
+pytest-benchmark==3.4.1
+Cython==0.29.27
+twine==1.15.0