Fix version of PyYAML. (#3240)

diff --git a/heron/executor/src/python/BUILD b/heron/executor/src/python/BUILD
index 993c384..fd5a5a7 100644
--- a/heron/executor/src/python/BUILD
+++ b/heron/executor/src/python/BUILD
@@ -7,7 +7,7 @@
         "//heron/statemgrs/src/python:statemgr-py",
         "//heron/common/src/python:common-py",
     ],
-    reqs = ["PyYAML==3.10"],
+    reqs = ["PyYAML==3.13"],
 )
 
 pex_binary(
diff --git a/heron/instance/src/python/BUILD b/heron/instance/src/python/BUILD
index ec6b916..706cfbd 100644
--- a/heron/instance/src/python/BUILD
+++ b/heron/instance/src/python/BUILD
@@ -19,6 +19,6 @@
     deps = [":instance-py"],
     reqs = [
         'colorlog==2.6.1',
-        'PyYAML==3.10'
+        'PyYAML==3.13'
     ]
 )
diff --git a/heron/statemgrs/src/python/BUILD b/heron/statemgrs/src/python/BUILD
index 5bce928..052ebd7 100644
--- a/heron/statemgrs/src/python/BUILD
+++ b/heron/statemgrs/src/python/BUILD
@@ -7,7 +7,7 @@
     '//heron/proto:proto-py',
   ],
   reqs = [
-    'PyYAML==3.10',
+    'PyYAML==3.13',
     'kazoo==1.3.1',
     'zope.interface==4.0.5'
   ],
diff --git a/heron/tools/admin/src/python/BUILD b/heron/tools/admin/src/python/BUILD
index cadeb7b..f3063c7 100644
--- a/heron/tools/admin/src/python/BUILD
+++ b/heron/tools/admin/src/python/BUILD
@@ -12,7 +12,7 @@
         "//heron/proto:proto-py",
     ],
     reqs = [
-      "PyYAML==3.10",
+      "PyYAML==3.13",
       "enum34==1.1.6",
       "requests==2.12.3",
       "netifaces==0.10.6"
diff --git a/heron/tools/cli/src/python/BUILD b/heron/tools/cli/src/python/BUILD
index f104f6f..1f33ab3 100644
--- a/heron/tools/cli/src/python/BUILD
+++ b/heron/tools/cli/src/python/BUILD
@@ -11,7 +11,7 @@
         "//heron/proto:proto-py",
     ],
     reqs = [
-      "PyYAML==3.10",
+      "PyYAML==3.13",
       "enum34==1.1.6",
       "requests==2.12.3",
       "netifaces==0.10.6"
diff --git a/heron/tools/common/src/python/BUILD b/heron/tools/common/src/python/BUILD
index 91f035e..699fe11 100644
--- a/heron/tools/common/src/python/BUILD
+++ b/heron/tools/common/src/python/BUILD
@@ -15,5 +15,5 @@
     deps = [
         "//heron/common/src/python:common-py",
     ],
-    reqs = ["PyYAML==3.10"],
+    reqs = ["PyYAML==3.13"],
 )