re6st: fix build on OS with Python 3

For CentOS_8 & CentOS_8_Stream, I give up:
- nothing provides python, python2, python3 or /usr/bin/python
  (actually, there's a python2 package on CentOS_8_Stream, but only to ship
  a /usr/bin/python2 that tells the user not to use Python 2... wtf ?)
- by default, there exists /usr/libexec/platform-python and it's functional
  but the build of openssl requires any of python{,2,3} in PATH, which means
  that a probable solution is to:
  - conditionally depend on 'python' only `%if 0%{?centos_ver} != 8`
  - change Makefile.in to add a symlink to /usr/libexec/platform-python
    in a temporary directory that we add to $PATH during the build
- ... but it's probably fine to use packages for CentOS_7

obs/re6st/Makefile.in

@@ -8,7 +8,7 @@
 BUILD = $(TARGET)
 
 PATH := $(CURDIR)/$(BUILD)/parts/chrpath/bin:$(CURDIR)/$(BUILD)/parts/file/bin:$(CURDIR)/$(BUILD)/parts/perl/bin:$(PATH)
-PYTHON2 = $(firstword $(wildcard /usr/bin/python2 /usr/bin/python))
+PYTHON = $(or $(shell command -v python2 || command -v python || command -v python3),$(error no Python found))
 
 all: $(BUILD)/.installed.cfg
 ifneq ($(wildcard upstream.mk),)
@@ -22,7 +22,7 @@ install: _install
 endif
 
 $(BUILD)/bin/buildout:
-	cd $(BUILD) && $(PYTHON2) -S $(CURDIR)/bootstrap
+	cd $(BUILD) && $(PYTHON) -S $(CURDIR)/bootstrap
 
 $(BUILD)/.installed.cfg: $(BUILD)/bin/buildout $(BUILD)/buildout.cfg
 	cd $(BUILD) && bin/buildout babeld-repository:recipe=
@@ -39,7 +39,7 @@ $(PROGS): $(BUILD)/.installed.cfg
 
 $(DESTDIR)/$(TARGET): $(BUILD)/.installed.cfg
 	rm -rf $@ && mkdir -p $@/parts
-	cd $(BUILD) && $(PYTHON2) $(CURDIR)/install-eggs $@ $(BIN)
+	cd $(BUILD) && $(PYTHON) $(CURDIR)/install-eggs $@ $(BIN)
 	for x in $(filter-out $(NOPART),$(shell cd $(BUILD)/parts && echo *)); \
 	do cp --preserve=links -r $(BUILD)/parts/$$x $@/parts; done
 	cd $@ && $(CURDIR)/cleanup && chmod -R u+w .

obs/re6st/install-eggs

-#!/usr/bin/python2
+#!/usr/bin/python
 import errno, os, shutil, sys
 
 path = set()
@@ -15,8 +15,9 @@ sys_path = sys.path
 try:
     sys.path = SysPath(sys_path)
     for x in sys.argv[2:]:
+        x = os.path.join("bin", x)
         try:
-            execfile(os.path.join("bin", x))
+            exec(compile(open(x, "rb").read(), x, 'exec'))
         except Stop:
             pass
 finally:

obs/re6st/make.py

@@ -207,7 +207,7 @@ def deb(task):
     d["Version"] = VERSION
     d["Architecture"] = b["Architecture"] = "any"
     d["Build-Depends"] = s["Build-Depends"] = (
-        "python (>= 2.7), debhelper (>= 9.20120909),"
+        "python (>= 2.7) | python2 | python3, debhelper (>= 9.20120909),"
         " debhelper (>= 10) | dh-systemd,"
         " iproute2 | iproute"
     )