09_git.ipynb: Using '!mkdir -p <directory>' is not portable

Replace it with pure-Python version, using Path.mkdir() from pathlib.

Author: jnareb

09_git.ipynb

@@ -151,18 +151,9 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stderr",
-     "output_type": "stream",
-     "text": [
-      "A subdirectory or file repos already exists.\n",
-      "Error occurred while processing: repos.\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
-    "!mkdir -p repos"
+    "Path(\"repos\").mkdir(exist_ok=True)"
    ]
   },
   {
@@ -194,17 +185,9 @@
    "cell_type": "code",
    "execution_count": null,
    "metadata": {},
-   "outputs": [
-    {
-     "name": "stderr",
-     "output_type": "stream",
-     "text": [
-      "A subdirectory or file datasets already exists.\n"
-     ]
-    }
-   ],
+   "outputs": [],
    "source": [
-    "!mkdir -p datasets"
+    "Path(\"datasets\").mkdir(exist_ok=True)"
    ]
   },
   {