Moved cache list creation into its own function

This begins work towards a more complete solution for #99, and allows
for the initialize function to be mocked / called separately when
working in tests.

pshtt/pshtt.py

@@ -897,7 +897,7 @@ def is_hsts_preload_pending(domain):
     "unknown".
     """
     if preload_pending is None:
-        return None
+        initialize_caches()
 
     return domain.domain in preload_pending
 
@@ -910,7 +910,7 @@ def is_hsts_preloaded(domain):
     "unknown".
     """
     if preload_list is None:
-        return None
+        initialize_caches()
 
     return domain.domain in preload_list
 
@@ -929,7 +929,7 @@ def parent_domain_for(hostname):
     If there is no suffix_list available, simply return the hostname
     """
     if suffix_list is None:
-        return hostname
+        initialize_caches()
 
     return suffix_list.get_public_suffix(hostname)
 
@@ -1140,6 +1140,19 @@ def csv_for(results, out_filename):
     out_file.close()
 
 
+def initialize_caches():
+    # Download HSTS preload list, caches locally.
+    global preload_list
+    preload_list = create_preload_list()
+
+    # Download HSTS pending preload list. Not cached.
+    global preload_pending
+    preload_pending = fetch_preload_pending()
+
+    global suffix_list
+    suffix_list = load_suffix_list()
+
+
 def inspect_domains(domains, options):
     # Override timeout, user agent, preload cache, default CA bundle
     global TIMEOUT, USER_AGENT, PRELOAD_CACHE, WEB_CACHE, SUFFIX_CACHE, CA_FILE, STORE
@@ -1170,16 +1183,7 @@ def inspect_domains(domains, options):
         # "Custom" Option from the sslyze output.
         STORE = "Custom"
 
-    # Download HSTS preload list, caches locally.
-    global preload_list
-    preload_list = create_preload_list()
-
-    # Download HSTS pending preload list. Not cached.
-    global preload_pending
-    preload_pending = fetch_preload_pending()
-
-    global suffix_list
-    suffix_list = load_suffix_list()
+    initialize_caches()
 
     # For every given domain, get inspect data.
     results = []