Only copy files in startup dir if we just created it.

Closes  #14496

IPython/core/profiledir.py

@@ -14,6 +14,8 b' from ..paths import get_ipython_package_dir'
 from ..utils.path import expand_path, ensure_dir_exists
 from traitlets import Unicode, Bool, observe
 
+from typing import Optional
+
 #-----------------------------------------------------------------------------
 # Module errors
 #-----------------------------------------------------------------------------
@@ -69,17 +71,30 b' class ProfileDir(LoggingConfigurable):'
         self.static_dir = os.path.join(new, self.static_dir_name)
         self.check_dirs()
     
-    def _mkdir(self, path, mode=None):
+    def _mkdir(self, path: str, mode: Optional[int] = None) -> bool:
         """ensure a directory exists at a given path
 
         This is a version of os.mkdir, with the following differences:
 
-        - returns True if it created the directory, False otherwise
+        - returns wether the directory has been created or not.
         - ignores EEXIST, protecting against race conditions where
           the dir may have been created in between the check and
           the creation
         - sets permissions if requested and the dir already exists
+
+        Parameters
+        ----------
+        path: str
+            path of the dir to create
+        mode: int
+            see `mode` of `os.mkdir`
+
+        Returns
+        -------
+        bool:
+            returns True if it created the directory, False otherwise
         """
+
         if os.path.exists(path):
             if mode and os.stat(path).st_mode != mode:
                 try:
@@ -109,13 +124,17 b' class ProfileDir(LoggingConfigurable):'
     
     @observe('startup_dir')
     def check_startup_dir(self, change=None):
-        self._mkdir(self.startup_dir)
-
-        readme = os.path.join(self.startup_dir, 'README')
-        src = os.path.join(get_ipython_package_dir(), u'core', u'profile', u'README_STARTUP')
+        if self._mkdir(self.startup_dir):
+            readme = os.path.join(self.startup_dir, "README")
+            src = os.path.join(
+                get_ipython_package_dir(), "core", "profile", "README_STARTUP"
+            )
 
         if not os.path.exists(src):
-            self.log.warning("Could not copy README_STARTUP to startup dir. Source file %s does not exist.", src)
+                self.log.warning(
+                    "Could not copy README_STARTUP to startup dir. Source file %s does not exist.",
+                    src,
+                )
 
         if os.path.exists(src) and not os.path.exists(readme):
             shutil.copy(src, readme)