Fix #568 with ENV var workaround

EDMC.py would break due to an import chain that ends up in theme. Theme
does a whole bunch of work to setup our GUI for EDMarketConnector.py,
but it does this on any import, which will fail spectacularly if there
is either no DISPLAY var set or no X11 libs available on our machine at
all (as a sidenote this means it probably also breaks on a wholly
wayland install).

This fixes the issue by adding a check for an environment variable on
import of theme. This can and WILL break if the env var is set and
EDMarketConnector.py is used, but if you do that its your own fault.

EDMC.py

@@ -8,6 +8,10 @@ import json
 import requests
 import sys
 import os
+
+# workaround for https://github.com/EDCD/EDMarketConnector/issues/568
+os.environ["EDMC_NO_UI"] = "1"
+
 from os.path import dirname, getmtime, join
 from time import time, sleep
 from xml.etree import ElementTree

theme.py

@@ -5,6 +5,7 @@
 # So can't use ttk's theme support. So have to change colors manually.
 #
 
+import os
 from sys import platform
 from os.path import join
 
@@ -18,6 +19,11 @@ from config import appname, applongname, config
 if __debug__:
     from traceback import print_exc
 
+if platform == "linux":
+    from ctypes import *
+
+
+def setup_UI__():
     if platform == 'win32':
         import ctypes
         from ctypes.wintypes import LPCWSTR, DWORD, LPCVOID
@@ -28,8 +34,6 @@ if platform == 'win32':
         AddFontResourceEx(join(config.respath, u'EUROCAPS.TTF'), FR_PRIVATE, 0)
 
     elif platform == 'linux':
-    from ctypes import *
-
         XID = c_ulong 	# from X.h: typedef unsigned long XID
         Window = XID
         Atom = c_ulong
@@ -67,6 +71,10 @@ elif platform == 'linux':
                 ('status', c_ulong),
             ]
         
+        # workaround for https://github.com/EDCD/EDMarketConnector/issues/568
+        if os.getenv("EDMC_NO_UI") :
+            return
+        
         try:
             xlib = cdll.LoadLibrary('libX11.so.6')
             XInternAtom = xlib.XInternAtom
@@ -87,6 +95,7 @@ elif platform == 'linux':
             dpy = xlib.XOpenDisplay(None)
             if not dpy:
                 raise Exception("Can't find your display, can't continue")
+            
             motif_wm_hints_property = XInternAtom(dpy, b'_MOTIF_WM_HINTS', False)
             motif_wm_hints_normal = MotifWmHints(MWM_HINTS_FUNCTIONS | MWM_HINTS_DECORATIONS,
                                                 MWM_FUNC_RESIZE | MWM_FUNC_MOVE | MWM_FUNC_MINIMIZE | MWM_FUNC_CLOSE,
@@ -379,5 +388,7 @@ class _Theme(object):
             self.minwidth = root.winfo_width()	# Minimum width = width on first creation
             root.minsize(self.minwidth, -1)
 
+
+setup_UI__()
 # singleton
 theme = _Theme()