Update test deps.

Author: ionelmc

tox.ini

@@ -3,8 +3,9 @@
 [tox]
 envlist =
     check
-    py{27,35,36,37,py,py3}-pytest46-xdist27-coverage{45,51}
-    py{36,37,38,py3}-pytest{46,54}-xdist32-coverage{45,51}
+    py{27,35,36,37,py,py3}-pytest46-xdist27-coverage{45,52}
+    py{36,37,38,py3}-pytest{46,54}-xdist33-coverage{45,52}
+    py{36,37,38,py3}-pytest{60}-xdist33-coverage{52}
     docs
 
 [testenv]
@@ -15,16 +16,19 @@ setenv =
     # Use env vars for (optional) pinning of deps.
     pytest46:  _DEP_PYTEST=pytest==4.6.10
     pytest53:  _DEP_PYTEST=pytest==5.3.2
-    pytest54:  _DEP_PYTEST=pytest==5.4.2
+    pytest54:  _DEP_PYTEST=pytest==5.4.3
+    pytest60:  _DEP_PYTEST=pytest==6.0.0rc1
 
     xdist27: _DEP_PYTESTXDIST=pytest-xdist==1.27.0
     xdist29: _DEP_PYTESTXDIST=pytest-xdist==1.29.0
     xdist31: _DEP_PYTESTXDIST=pytest-xdist==1.31.0
     xdist32: _DEP_PYTESTXDIST=pytest-xdist==1.32.0
+    xdist33: _DEP_PYTESTXDIST=pytest-xdist==1.33.0
 
     coverage45: _DEP_COVERAGE=coverage==4.5.4
     coverage50: _DEP_COVERAGE=coverage==5.0.4
     coverage51: _DEP_COVERAGE=coverage==5.1
+    coverage52: _DEP_COVERAGE=coverage==5.2
     # For testing against a coverage.py working tree.
     coveragedev: _DEP_COVERAGE=-e{env:COVERAGE_HOME}
 passenv =