gh-38826: src/sage/env.py: canonicalize paths in a test
A test in sage.env is running sage in a subprocess to compare the values
of `SAGE_ROOT` and `SAGE_LOCAL`. It does the comparison as strings,
however, and can fail:
```
File "src/sage/env.py", line 14, in sage.env
Failed example:
out == repr((SAGE_ROOT, SAGE_LOCAL)) # long time
Expected:
True
Got:
False
```
This despite the fact that both values are equivalent:
```
sage: out
"('/home/mjo/src/sage.git/src/sage/../..', '/usr')"
sage: repr((SAGE_ROOT, SAGE_LOCAL))
"('/home/mjo/src/sage.git', '/usr')"
```
We update the test to canonicalize the paths within the subprocess, and
output only "True" or "False" instead.
URL: https://github.com/sagemath/sage/pull/38826
Reported by: Michael Orlitzky
Reviewer(s): Tobias Diez
