Override LANGUAGE when running tests

Apparently LANGUAGE has precedence over LC_ALL. By setting it to an
empty string, LC_ALL takes precedence again, and we forcefully use the
English translations.

Signed-off-by: Carmen Bianca BAKKER <carmenbianca@fsfe.org>

tests/conftest.py

@@ -28,6 +28,7 @@
 from jinja2 import Environment
 
 os.environ["LC_ALL"] = "C"
+os.environ["LANGUAGE"] = ""
 
 # A trick that tries to import the installed version of reuse. If that doesn't
 # work, import from the src directory. If that also doesn't work (for some