Me desarrollo para ambosPython 2 y3.
Por lo tanto, tengo que usar ambospip2 ypip3.

Cuando usaspip3 - Recibo esta solicitud de actualización (últimas dos líneas):

$ pip3 install arrow
Requirement already satisfied (use --upgrade to upgrade): arrow in c:\program files (x86)\python3.5.1\lib\site-packages
Requirement already satisfied (use --upgrade to upgrade): python-dateutil in c:\program files (x86)\python3.5.1\lib\site-packages (from arrow)
Requirement already satisfied (use --upgrade to upgrade): six>=1.5 in c:\program files (x86)\python3.5.1\lib\site-packages (from python-dateutil->arrow)
You are using pip version 7.1.2, however version 8.1.2 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

Mi defectopip es paraPython 2, a saber:

$  python -m pip install --upgrade pip
Requirement already up-to-date: pip in /usr/lib/python2.7/site-packages

Sin embargo, ninguno de los siguientesexplícito los comandos tienen éxito al actualizar elPython 3 pip:

$  python -m pip3 install --upgrade pip3
/bin/python: No module named pip3

$  python -m pip install --upgrade pip3
Collecting pip3
  Could not find a version that satisfies the requirement pip3 (from versions: )
No matching distribution found for pip3

$  python -m pip install --upgrade pip3.4
Collecting pip3.4
  Could not find a version that satisfies the requirement pip3.4 (from versions: )
No matching distribution found for pip3.4

¿Cuál es el comando correcto para actualizar pip3 cuando no es el pip predeterminado?

Ambiente:

$ python3 -V
Python 3.4.3
$ uname -a
CYGWIN_NT-6.1-WOW 2.5.2(0.297/5/3) 2016-06-23 14:27 i686 Cygwin