Pythonista is based on CPython 2.7.5 but the current CPython is 2.7.11. It you go back and read the URLs that you provided above, you will see that urllib3 warns you if you are doing certain things with CPython versions prior to 2.7.9.
Thank you for the version numbers -- that explains a lot. I reported this since these exceptions were not popping up in Pythonista 2.0 but started with 2.1. I'm upgrading code to Dropbox v2, but will just disable these warnings in the current v1 code.