Can't enable debug mode

[timhoffm]

Description of your problem

Spyder won't start in debug mode anymore. Several weeks ago this was working. It's broken now for a couple of weeks. Don't know the exact time when that changed. This affects branches 3.x as well as master.

What steps will reproduce the problem?

1. run bootstrap.py --debug

What is the expected output? What do you see instead?
Expected: Spyder should start up.
Instead: The program terminates with the message "ERROR: Can't enable debug mode - Spyder is already imported"

Please provide any additional information below

Debug mode will only be started if not "spyder.config.base" in sys.modules. However it seems that from spyder.utils.vcs import get_git_revision some lines earlier in bootstrap.py does always add this module to sys.modules.

I propose to move the code for enabling debugging up before the version information.

Version and main components

• Spyder Version: 4.0.0.dev0 42175ba
• Python Version: 3.6.3
• Qt Versions: 5.6.2, PyQt5 5.6 on Windows

Dependencies

pyflakes >=0.6.0 :  1.6.0 (OK)
pycodestyle >=2.3:  2.3.1 (OK)
pygments >=2.0   :  2.2.0 (OK)
pandas >=0.13.1  :  0.20.3 (OK)
numpy >=1.7      :  1.13.3 (OK)
sphinx >=0.6.6   :  1.6.3 (OK)
rope >=0.9.4     :  0.10.5 (OK)
jedi >=0.9.0     :  0.10.2 (OK)
nbconvert >=4.0  :  5.3.1 (OK)
sympy >=0.7.3    :  1.1.1 (OK)
cython >=0.21    :  0.26.1 (OK)
qtconsole >=4.2.0:  4.3.1 (OK)
IPython >=4.0    :  6.1.0 (OK)
pylint >=0.25    :  1.7.4 (OK)