diff -up src/sage/env.py.orig src/sage/env.py
--- src/sage/env.py.orig	2019-04-08 12:41:09.686920533 -0600
+++ src/sage/env.py	2019-04-08 12:42:41.240282849 -0600
@@ -159,9 +159,9 @@ var('SAGE_DOC',            join(SAGE_SHA
 var('SAGE_SPKG_INST',      join(SAGE_LOCAL, 'var', 'lib', 'sage', 'installed'))
 var('SAGE_LIB',            os.path.dirname(os.path.dirname(sage.__file__)))
 
-var('SAGE_ROOT')           # no fallback for SAGE_ROOT
+var('SAGE_ROOT',           '@@SAGE_ROOT@@')
 var('SAGE_SRC',            join(SAGE_ROOT, 'src'), SAGE_LIB)
-var('SAGE_DOC_SRC',        join(SAGE_SRC, 'doc'))
+var('SAGE_DOC_SRC',        '@@SAGE_DOC@@')
 var('SAGE_PKGS',           join(SAGE_ROOT, 'build', 'pkgs'))
 var('SAGE_ROOT_GIT',       join(SAGE_ROOT, '.git'))