problem installing sage on ubuntu18.04

edit

As written on the download page, I wanted to get the linux binaries. I can't find them. I've obtained the source tarball for ubuntu18.4 (64bits).

I've unarchived the directory Sagemath and cd'ed there. I type make as explained. This is the message I obtain:

RecursionError: maximum recursion depth exceeded during compilation Makefile:31: recipe for target 'base-toolchain' failed make: * [base-toolchain] Error 1

I've tried to install sage via apt with sudo apt install sagemath-common all goes well, no error message. Then try to run sage and obtain the following message:

│ SageMath version 8.1, Release Date: 2017-12-07 │ │ Type "notebook()" for the browser-based notebook interface.
│ │ Type "help()" for help.
│ Traceback (most recent call last):
File "/usr/share/sagemath/bin/sage-ipython", line 7, in <module> from sage.repl.interpreter import SageTerminalApp ImportError: No module named 'sage'

I had a working sage (7.?) on the same machine under ubuntu16.04 which stopped working under ubuntu18.04. I've deleted the Sage and also the .sage directories before trying all the above.

I am at my wit's end and would greatly appreciate any help.