[requires.io] dependency update

tox.ini

@@ -59,9 +59,9 @@ deps =
     pytest-cov==2.9.0
 
     # For hypothesis. Note Python 3.4 isn't supported by hypothesis.
-    py27: hypothesis==4.43.9  # rq.filter: <4.44
+    py27: hypothesis==4.43.9
     {py35,py36,py37,py38,py39,py2,py3}: hypothesis==5.8.6
-    py27: mock==3.0.5
+    py27: mock==4.0.2
 
 setenv =
     {[default]setenv}
@@ -246,7 +246,7 @@ basepython = {[default]basepython}
 skip_install = True
 
 deps =
-    coverage==4.5.4  # rq.filter: <5  # coverage 5.0 drops Python 3.4 support
+    coverage==5.1
 
 setenv =
     {[default]setenv}
@@ -317,7 +317,7 @@ description = build documentation
 basepython = {[default]basepython}
 
 deps =
-    Sphinx==3.0.4
+    Sphinx==3.1.0
     sphinx-rtd-theme==0.4.3
 
 commands =