• Pip version: pip 9.0.3 from c:\python36\lib\site-packages (python 3.6)
• Python version: Python 3.6.2
• Operating system: Windows 10

Description:

In #5168 I learned that version numbers like "2018.04.04a" are interpreted as pre-release versions. Therefore I could not install them without adding the parameter --pre.

However, this is implicit knowledge the user must have about interpretations of version numbers and related pip behavior in order to understand the behavior of pip. Otherwise, the user is irritated, just like I was until a couple of minutes ago.

Current situation where 2018.04.04a is not installable when --pre is not given:

C:\Users\karl.voit>pip search filetags
filetags (2018.04.04a)  - Management of simple tags within file names
  INSTALLED: 2018.3.19
  LATEST:    2018.04.04a

C:\Users\karl.voit>

Shouldn't there at least be a hint such as following suggestion?

C:\Users\karl.voit>pip search filetags
filetags (2018.04.04a)  - Management of simple tags within file names
  INSTALLED: 2018.3.19
  LATEST:    2018.04.04a (pre-release; install with "pip install --pre")

C:\Users\karl.voit>

Maybe this applies for multiple stdout messages.

What I've run:

See #5168 to give you some background.