development/test requirements: pin versions

hopefully avoids future breakage.

requirements.d/development.lock.txt

@@ -1,9 +1,20 @@
 virtualenv==13.1.2
+wheel==0.24.0
 setuptools-scm==3.1.0
 pluggy==0.6.0
+apipkg==1.5
+attrs==18.2.0
+more-itertools==6.0.0
+packaging==19.0
+pyparsing==2.3.1
 tox==3.1.3
+py==1.7.0
 pytest==3.5.1
+execnet==1.5.0
+pytest-forked==1.0.2
 pytest-xdist==1.24.0
+coverage==4.5.2
 pytest-cov==2.6.0
+py-cpuinfo==4.0.0
 pytest-benchmark==3.1.1
 Cython==0.29