Using python2.7 Tkinter for executing Tcl.
The Tcl code has package require Tcl 8.5, while the tclsh loads Tcl 8.4 by default.
Causes: version conflict for package "Tcl": have 8.4, need 8.5
I have libtcl8.5.so installed at a custom location.
Tried adding it to LD_LIBRARY_PATH, TCL_LIBRARY, TCLLIBPATH. Nothing worked. It's like the tclsh completely ignores the envs.
What worked eventually:

    tcl = Tkinter.tcl()
    tcl.eval('package forget Tcl')
    tcl.eval('package provide Tcl 8.5')
    tcl.eval('package require Tcl')
    8.5
Success!
Python Tkinter: version conflict for package "Tcl": have 8.4, need 8.5