Update __main__.py with f-strings instead of %s strings (#1906)

sherlock/__main__.py

@@ -15,7 +15,7 @@
     python_version = sys.version.split()[0]
 
     if sys.version_info < (3, 6):
-        print("Sherlock requires Python 3.6+\nYou are using Python %s, which is not supported by Sherlock" % (python_version))
+        print(f"Sherlock requires Python 3.6+\nYou are using Python {python_version}, which is not supported by Sherlock.")
         sys.exit(1)
 
     import sherlock