Resolve application path with shutil.which

Addresses non-intuitive behavior of `dotenv run python ...` on Windows

src/dotenv/cli.py

@@ -1,6 +1,7 @@
 import json
 import os
 import shlex
+import shutil
 import sys
 from contextlib import contextmanager
 from subprocess import Popen
@@ -189,6 +190,11 @@ def run_command(command: List[str], env: Dict[str, str]) -> int:
     cmd_env = os.environ.copy()
     cmd_env.update(env)
 
+    # Resolve path in a consistent way
+    app = shutil.which(command[0])
+    if app is not None:
+        command = (app,) + command[1:]
+
     p = Popen(command,
               universal_newlines=True,
               bufsize=0,