Insist on Python 3.6, since the 'secrets' module for making secure tokens isn't available in 3.5

Pipfile

@@ -4,6 +4,9 @@ url = "https://pypi.python.org/simple"
 verify_ssl = true
 name = "pypi"
 
+[requires]
+python_version = '3.6'
+
 
 [packages]
 

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "c9835b77b96ade2202ff84521a2cda6a3c04679d448cc434a49f3ce07d6befcf"
+            "sha256": "8d981d3d640ab95689a05ffd6aae4fd372a8fbe566b4e8c3caf8de2a6d3dd4e9"
         },
         "host-environment-markers": {
             "implementation_name": "cpython",
@@ -17,7 +17,9 @@
             "sys_platform": "darwin"
         },
         "pipfile-spec": 6,
-        "requires": {},
+        "requires": {
+            "python_version": "3.6"
+        },
         "sources": [
             {
                 "name": "pypi",
@@ -178,10 +180,10 @@
         },
         "html5lib": {
             "hashes": [
-                "sha256:08a3efc117a4fc8c82c3c6d10d6f58ae266428d57ed50258a1466d2cd88de745",
+                "sha256:b8934484cf22f1db684c0fae27569a0db404d0208d20163fbf51cc537245d008",
-                "sha256:0d5fd54d5b2b79b876007a70c033a4023577768d18022c15681c00561432a0f9"
+                "sha256:ee747c0ffd3028d2722061936b5c65ee4fe13c8e4613519b4447123fc4546298"
             ],
-            "version": "==1.0b10"
+            "version": "==0.999999999"
         },
         "idna": {
             "hashes": [