replace percent formatters with f-strings

fancycompleter/__init__.py

@@ -428,9 +428,9 @@ def __init__(self, basepath, force):
     def check(self):
         PYTHONSTARTUP = os.environ.get("PYTHONSTARTUP")
         if PYTHONSTARTUP:
-            return "PYTHONSTARTUP already defined: %s" % PYTHONSTARTUP
+            return f"PYTHONSTARTUP already defined: {PYTHONSTARTUP}"
         if os.path.exists(self.filename):
-            return "%s already exists" % self.filename
+            return f"{self.filename} already exists"
 
     def install(self):
         import textwrap
@@ -454,12 +454,12 @@ def install(self):
 
     def set_env_var(self):
         if sys.platform == "win32":
-            os.system('SETX PYTHONSTARTUP "%s"' % self.filename)
-            print("%PYTHONSTARTUP% set to", self.filename)
+            os.system(f'SETX PYTHONSTARTUP "{self.filename}"')
+            print(f"%PYTHONSTARTUP% set to {self.filename}")
         else:
-            print("startup file written to", self.filename)
+            print(f"startup file written to {self.filename}")
             print("Append this line to your ~/.bashrc:")
-            print("    export PYTHONSTARTUP=%s" % self.filename)
+            print(f"    export PYTHONSTARTUP={self.filename}")
 
 
 if __name__ == "__main__":

tests/test_configurableclass.py

@@ -35,7 +35,7 @@ class MyCfg(ConfigurableClass):
     out, err = capsys.readouterr()
     assert out == ""
     assert err == (
-        "** error when setting up Config from ~/.mycfg: my_exc (%s:1) **\n" % p
+        f"** error when setting up Config from ~/.mycfg: my_exc ({p}:1) **\n"
     )
 
     # Error during execfile.