diff -up src/sage/env.py.orig src/sage/env.py
--- src/sage/env.py.orig	2017-11-08 08:27:50.523217592 -0500
+++ src/sage/env.py	2017-11-08 08:27:58.147217884 -0500
@@ -90,7 +90,7 @@ _add_variable_or_fallback('HOSTNAME',
 _add_variable_or_fallback('LOCAL_IDENTIFIER','$HOSTNAME.%s'%os.getpid())
 
 # bunch of sage directories and files
-_add_variable_or_fallback('SAGE_ROOT',       None)
+_add_variable_or_fallback('SAGE_ROOT',       '@@SAGE_ROOT@@')
 _add_variable_or_fallback('SAGE_LOCAL',      None)
 _add_variable_or_fallback('SAGE_ETC',        opj('$SAGE_LOCAL', 'etc'))
 _add_variable_or_fallback('SAGE_INC',        opj('$SAGE_LOCAL', 'include'))
@@ -116,7 +116,7 @@ _add_variable_or_fallback('SAGE_PKGS', o
 _add_variable_or_fallback('SAGE_EXTCODE',    opj('$SAGE_SHARE', 'sage', 'ext'))
 _add_variable_or_fallback('SAGE_LOGS',       opj('$SAGE_ROOT', 'logs', 'pkgs'))
 _add_variable_or_fallback('SAGE_SPKG_INST',  opj('$SAGE_LOCAL', 'var', 'lib', 'sage', 'installed'))
-_add_variable_or_fallback('SAGE_DOC_SRC',    opj('$SAGE_SRC', 'doc'))
+_add_variable_or_fallback('SAGE_DOC_SRC',    '@@SAGE_DOC@@')
 _add_variable_or_fallback('SAGE_DOC',        opj('$SAGE_SHARE', 'doc', 'sage'))
 _add_variable_or_fallback('DOT_SAGE',        opj(os.environ.get('HOME','$SAGE_ROOT'), '.sage'))
 _add_variable_or_fallback('SAGE_DOT_GIT',    opj('$SAGE_ROOT', '.git'))