[MacPorts] #60887: certbot: Use python38 by default

[MacPorts]

#60887: certbot: Use python38 by default
-------------------------+-------------------------
 Reporter:  ryandesign   |      Owner:  Schamschula
     Type:  enhancement  |     Status:  assigned
 Priority:  Normal       |  Milestone:
Component:  ports        |    Version:
 Keywords:               |       Port:  certbot
-------------------------+-------------------------
 The certbot port currently enables the python37 variant by default. Please
 change that to python38 because that is the latest stable version.

 Also, the order of lines in the portfile looks incorrect. Starting at line
 22, you check which python variant is selected and act upon it:

 {{{
 if {[variant_isset python27]} {
     python.default_version 27
 } elseif {[variant_isset python36]} {
     python.default_version 36
 } elseif {[variant_isset python38]} {
     python.default_version 38
 } else {
     python.default_version 37
 }
 }}}

 But later in the portfile on line 73 you possibly change which variant is
 selected, making the earlier determinations inaccurate:

 {{{
 if {![variant_isset python27] && ![variant_isset python36] &&
 ![variant_isset python38]} {
     default_variants +python37
 }
 }}}

 In fact this probably works fine, but looks brittle because it requires
 the developer to change 37 to 38 in two places; if the developer only
 changes one, the port probably misbehaves. It would be good to fix it so
 that the default python version need only be specified in one place.

-- 
Ticket URL: <https://trac.macports.org/ticket/60887>
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