fix(resolve_exe): typecast exe name to string before passing to _resolve (#2457)

This PR aims to address #2455. The issue is related to an edge case wherein a missing executable that is being passed to resolve_exe is provided as a pathlib.Path object.

Author: martclanor

flopy/mbase.py

@@ -71,7 +71,7 @@ def _resolve(exe_name, checked=set()):
         checked.add(exe_name)
 
         # exe_name is found (not None), ensure absolute path is returned
-        if exe := which(str(exe_name)):
+        if exe := which(exe_name):
             return which(str(Path(exe).resolve()))
 
         # exe_name is relative path
@@ -88,7 +88,7 @@ def _resolve(exe_name, checked=set()):
         elif on_windows and "." not in Path(exe_name).stem:
             return _resolve(f"{exe_name}.exe", checked)
 
-    exe_path = _resolve(exe_name)
+    exe_path = _resolve(str(exe_name))
 
     # raise if we are unforgiving, otherwise return None
     if exe_path is None: