Eu desenvolvo para ambosPython 2 e3.
Então, eu tenho que usar ambospip2 epip3.

Ao usarpip3 - Recebo esta solicitação de atualização (duas últimas linhas):

$ 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.

Meu padrãopip é paraPython 2, nomeadamente:

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

No entanto, nenhum dos seguintesexplícito comandos conseguem atualizar oPython 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

Qual é o comando correto para atualizar o pip3 quando este não é o pip padrão?

Meio 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