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I tried to upgrade from fedora 25 to fedora 27. When running

sudo dnf system-upgrade download --releasever=27 --allowerasing

I encountered a transaction check error regarding python. The error summary can be found here

I paste here the first five lines

 file /usr/lib/python2.7/site-packages/IPython/__init__.py from install of python2-ipython-5.5.0-1.fc27.noarch conflicts with file from package python-ipython-console-3.2.1-8.fc25.noarch
 file /usr/lib/python2.7/site-packages/IPython/core/magics/__init__.py from install of python2-ipython-5.5.0-1.fc27.noarch conflicts with file from package python-ipython-console-3.2.1-8.fc25.noarch
 file /usr/lib/python2.7/site-packages/IPython/kernel/__init__.py from install of python2-ipython-5.5.0-1.fc27.noarch conflicts with file from package python-ipython-console-3.2.1-8.fc25.noarch
 file /usr/lib/python2.7/site-packages/IPython/__init__.pyc from install of python2-ipython-5.5.0-1.fc27.noarch conflicts with file from package python-ipython-console-3.2.1-8.fc25.noarch
 file /usr/lib/python2.7/site-packages/IPython/core/__init__.pyc from install of python2-ipython-5.5.0-1.fc27.noarch conflicts with file from package python-ipython-console-3.2.1-8.fc25.noarch

Any idea on how to overcome this issue and upgrade?

Had exact same issue. Not as complex as it seems. You first need to do:
sudo dnf remove python-ipython-console

Then proceed with
sudo dnf system-upgrade download --releasever=27 --allowerasing
which will automatically reinstall ipython (which I presume was a faulty install).

I'm not sure offhand what's causing this particular issue, but a general approach which works in most cases is: remove the package that's causing the problem, and add it back after the upgrade.

Of course, this doesn't work if it's a core package which can't be removed without breaking the system, and it's inconvenient if it's a package which a lot of things require, but neither of those should be the case with python-ipython-console.

I am having the same issue, but I think I have tracked down the problem. First, a question for you: are you using Sage? (package sagemath) The Sage packages require ipython-console, but they seem to have something wrong with their dependencies. It seems like the Sage packages aren't recognizing the new version of ipython-console in F27, so in the upgrade from F25, Sage is still expecting to see the older version of ipython-console. The result is that the upgrade fails due to file conflicts. The suggestion to remove ipython-console, then upgrade, seems right, but you need to be aware that you will also be uninstalling Sage and will need to reinstall it, too. Backing up your Sage data before any of this would probably be a good idea.