Upgrade requests_mock to 1.5.2 (#15867)

requirements_test.txt

@@ -14,4 +14,4 @@ pytest-cov==2.5.1
 pytest-sugar==0.9.1
 pytest-timeout==1.3.1
 pytest==3.7.1
-requests_mock==1.5
+requests_mock==1.5.2

requirements_test_all.txt

@@ -15,7 +15,7 @@ pytest-cov==2.5.1
 pytest-sugar==0.9.1
 pytest-timeout==1.3.1
 pytest==3.7.1
-requests_mock==1.5
+requests_mock==1.5.2
 
 
 # homeassistant.components.homekit