Try this way for sympy requirements

mvdoc · mvdoc · commit 31d93e51f077 · 2020-10-09T11:46:19.000-07:00
diff --git a/nipy/info.py b/nipy/info.py
@@ -170,7 +170,7 @@
 MICRO               = _version_micro
 ISRELEASE           = _version_extra == ''
 VERSION             = __version__
-REQUIRES            = ["numpy", "scipy", "sympy<1.6", "nibabel"]
+REQUIRES            = ["numpy", "scipy", "sympy(<1.6)", "nibabel"]
 STATUS              = 'beta'
 
 # Versions and locations of optional data packages
