Update pytest-xdist to 1.18.2 (#132)

* Update pytest-xdist from 1.18.1 to 1.18.2

* Update pytest-xdist from 1.18.1 to 1.18.2

requirements/py27-tests.txt

@@ -3,5 +3,5 @@ mozlog==3.5
 pytest==3.1.3
 pytest-metadata==1.5.0
 pytest-selenium==1.11.0
-pytest-xdist==1.18.1
+pytest-xdist==1.18.2
 selenium==3.4.3

requirements/py36-tests.txt

@@ -2,5 +2,5 @@ mock==2.0.0
 pytest==3.1.3
 pytest-metadata==1.5.0
 pytest-selenium==1.11.0
-pytest-xdist==1.18.1
+pytest-xdist==1.18.2
 selenium==3.4.3