mip: Avoid str.rpartition for limited builds.

ESP8266 disables str.partition and str.rpartition to save flash, so
installing a package manifest currently fails when deriving its base URL.
Use rfind and slicing instead, preserving the empty prefix when no slash
is present. This avoids requiring partition support on limited builds
without removing the on-device package installer.

Bump mip to version 0.5.1.

See micropython/micropython#19844

Signed-off-by: Matt Trentini <matt.trentini@gmail.com>

Author: mattytrentini

micropython/mip/manifest.py

@@ -1,4 +1,4 @@
-metadata(version="0.5.0", description="On-device package installer for network-capable boards")
+metadata(version="0.5.1", description="On-device package installer for network-capable boards")
 
 require("requests")
 

micropython/mip/mip/__init__.py

@@ -121,7 +121,9 @@ def _install_json(package_json_url, index, target, version, mpy):
             if not _download_file(file_url, fs_target_path):
                 print("File not found: {} {}".format(target_path, short_hash))
                 return False
-    base_url = package_json_url.rpartition("/")[0]
+    # str.rpartition is not available on all builds.
+    slash = package_json_url.rfind("/")
+    base_url = package_json_url[:slash] if slash >= 0 else ""
     for target_path, url in package_json.get("urls", ()):
         fs_target_path = target + "/" + target_path
         is_full_url = any(url.startswith(p) for p in _ALLOWED_MIP_URL_PREFIXES)