Merge branches 'guile-c11' and 'python-ci-fix'

Fix Travis CI builds broken due to the changes in Travis CI build
environment since the last successful build.

See #1798, #1799.
diff --git a/Examples/test-suite/python/Makefile.in b/Examples/test-suite/python/Makefile.in
index be06f7e..4c0507c 100644
--- a/Examples/test-suite/python/Makefile.in
+++ b/Examples/test-suite/python/Makefile.in
@@ -11,7 +11,7 @@
 LANGUAGE     = python
 PYTHON       = $(PYBIN)
 PYCODESTYLE       = @PYCODESTYLE@
-PYCODESTYLE_FLAGS = --ignore=E252,E30,E402,E501,E731,W291,W391
+PYCODESTYLE_FLAGS = --ignore=E252,E30,E402,E501,E731,E741,W291,W391
 
 #*_runme.py for Python 2.x, *_runme3.py for Python 3.x
 PY2SCRIPTSUFFIX = _runme.py
diff --git a/configure.ac b/configure.ac
index b4cadef..ab7de51 100644
--- a/configure.ac
+++ b/configure.ac
@@ -622,7 +622,7 @@
     PYEPREFIX=`($PYTHON -c "import sys; sys.stdout.write(sys.exec_prefix)") 2>/dev/null`
     AC_MSG_RESULT($PYEPREFIX)
 
-    if test x"$PYOSNAME" = x"nt" -a x"$PYSEPARATOR" = x"\\"; then
+    if test x"$PYOSNAME" = x"nt" -a x"$PYSEPARATOR" = x'\\'; then
       # Windows installations are quite different to posix installations (MinGW path separator is a forward slash)
       PYPREFIX=`echo "$PYPREFIX" | sed -e 's,\\\\,/,g'` # Forward slashes are easier to use and even work on Windows most of the time
       PYTHON_SO=.pyd
@@ -739,7 +739,7 @@
     PYVER=0
   fi
   if test "x$PY3BIN" = xyes; then
-    if test x"$PYOSNAME" = x"nt" -a x"$PYSEPARATOR" = x"\\" -a $PYVER -ge 3; then
+    if test x"$PYOSNAME" = x"nt" -a x"$PYSEPARATOR" = x'\\' -a $PYVER -ge 3; then
       PYTHON3="$PYTHON"
     else
       for py_ver in 3 3.9 3.8 3.7 3.6 3.5 3.4 3.3 3.2 ""; do
@@ -774,7 +774,7 @@
     PYSEPARATOR=`($PYTHON3 -c "import sys, os; sys.stdout.write(os.sep)") 2>/dev/null`
     AC_MSG_RESULT($PYSEPARATOR)
 
-    if test x"$PY3OSNAME" = x"nt" -a x"$PYSEPARATOR" = x"\\"; then
+    if test x"$PY3OSNAME" = x"nt" -a x"$PYSEPARATOR" = x'\\'; then
       # Windows installations are quite different to posix installations
       # There is no python-config to use
       AC_MSG_CHECKING(for Python 3.x prefix)