Use rdflib < 5.0.0 as it removed the parsers

Author: lopuhin

requirements.txt

@@ -2,7 +2,7 @@
 # pip install -r requirements.txt
 lxml
 requests
-rdflib
+rdflib<5.0.0
 rdflib-jsonld
 mf2py>=1.1.0
 six>=1.11

setup.py

@@ -28,10 +28,10 @@ def get_version():
     },
     packages=find_packages(exclude=['tests',]),
     package_data={'extruct': ['VERSION']},
-    install_requires=['lxml', 
-                      'rdflib', 
-                      'rdflib-jsonld', 
-                      'mf2py', 
+    install_requires=['lxml',
+                      'rdflib<5.0.0',
+                      'rdflib-jsonld',
+                      'mf2py',
                       'w3lib',
                       'html-text>=0.5.1',
                       'six'],