use filecache extra for Cachecontrol to get the correct dependency (#597)

Author: mr-c

requirements.txt

@@ -4,6 +4,5 @@ rdflib>= 4.2.2, < 7.0.0
 rdflib>= 4.2.2, < 6.0.0;python_version<='3.6'
 rdflib-jsonld>=0.4.0, <= 0.6.1;python_version<='3.6'
 mistune>=0.8.1,<0.9
-CacheControl==0.12.11
-lockfile==0.12.2  # needed for CacheControl's FileCache
+CacheControl[filecache]==0.12.11
 black

setup.py

@@ -88,8 +88,7 @@
     "rdflib >= 4.2.2, < 7.0.0",
     "rdflib-jsonld>=0.4.0, <= 0.6.1;python_version<='3.6'",
     "mistune >= 0.8.1, < 0.9",
-    "CacheControl >= 0.11.7, < 0.13",
-    "lockfile >= 0.9",  # needed for CacheControl's FileCache
+    "CacheControl[filecache] >= 0.11.7, < 0.13",
 ]
 
 extras_require = {