Merge branch 't/30008/after__30053__sphinx_3_1_2_does_not_build_on_ub…

…untu__trusty_xenial_bionic___debian_jessie__centos_7__again_' into t/30576/public/30576

build/bin/sage-system-python

@@ -28,6 +28,16 @@ fi
 # is accessible by this python; this is to guard on Cygwin against Pythons
 # installed somewhere else in Windows.
 
+# Trac #30008: Make it work even if the environment tries to sabotage UTF-8
+# operation in Python 3.0.x-3.6.x by setting LC_ALL=C or similar.
+
+if [ "$LC_ALL" = "C" -o "$LANG" = "C" -o "$LC_CTYPE" = "C" ]; then
+    LC_ALL=$(locale -a | grep -E -i '^(c|en_us)[-.]utf-?8$' | head -n 1)
+    LANG=$LC_ALL
+    export LC_ALL
+    export LANG
+fi
+
 PYTHONS="python python3 python3.8 python3.7 python2.7 python3.6 python2"
 for PY in $PYTHONS; do
     PYTHON="$(PATH="$SAGE_ORIG_PATH" command -v $PY)"

build/sage_bootstrap/uncompress/tar_file.py

@@ -28,8 +28,10 @@
 
 class SageBaseTarFile(tarfile.TarFile):
     """
-    Sage as tarfile.TarFile, but applies a reasonable umask (0022) to the
-    permissions of all extracted files and directories.
+    Same as tarfile.TarFile, but applies a reasonable umask (0022) to the
+    permissions of all extracted files and directories, and fixes
+    the encoding of file names in the tarball to be 'utf-8' instead of
+    depending on locale settings.
 
     Previously this applied the user's current umask per the default behavior
     of the ``tar`` utility, but this did not provide sufficiently reliable
@@ -46,6 +48,9 @@ class SageBaseTarFile(tarfile.TarFile):
     umask = 0o022
 
     def __init__(self, *args, **kwargs):
+
+        kwargs['encoding'] = 'utf-8'
+
         # Unfortunately the only way to get the current umask is to set it
         # and then restore it
         super(SageBaseTarFile, self).__init__(*args, **kwargs)