Use gramps.gen.const.HOME_DIR instead of os.environ['HOME']

$HOME doesn't exist on Windows, so os.environ['HOME'] gives the wrong answer.
(cherry picked from commit 53c878aa08)

gramps/gen/db/write.py

@@ -32,7 +32,7 @@ This is used since GRAMPS version 3.0
 # Standard python modules
 #
 #-------------------------------------------------------------------------
-from __future__ import print_function, with_statement
+from __future__ import print_function, with_statement, unicode_literals
 import sys
 if sys.version_info[0] < 3:
     import cPickle as pickle
@@ -81,7 +81,7 @@ from ..updatecallback import UpdateCallback
 from ..errors import DbError
 from ..constfunc import (win, conv_to_unicode, cuni, UNITYPE, handle2internal,
                          get_env_var)
-from ..const import GRAMPS_LOCALE as glocale
+from ..const import HOME_DIR, GRAMPS_LOCALE as glocale
 _ = glocale.translation.gettext
 
 _LOG = logging.getLogger(DBLOGNAME)
@@ -2276,7 +2276,7 @@ def write_lock_file(name):
         try:
             user = os.getlogin()
         except:
-            user = get_env_var('USER')
+            user = os.environ['USER'] #not win, don't need get_env_var
     if host:
         text = "%s@%s" % (user, host)
     else:
@@ -2302,7 +2302,7 @@ if __name__ == "__main__":
     if len(sys.argv) > 1:
         db_name = sys.argv[1]
     else:
-        db_home = os.path.join(os.environ['HOME'], '.gramps','grampsdb')
+        db_home = os.path.join(HOME_DIR,'grampsdb')
         for dir in os.listdir(db_home):
             db_path = os.path.join(db_home, dir)
             db_fn = os.path.join(db_path, 'name.txt')

gramps/gui/configure.py

@@ -1407,7 +1407,7 @@ class GrampsPreferences(ConfigureDialog):
                      Gtk.ResponseType.OK))
         dbpath = config.get('behavior.database-path')
         if not dbpath:
-            dbpath = os.path.join(os.environ['HOME'], '.gramps','grampsdb')
+            dbpath = os.path.join(HOME_DIR,'grampsdb')
         f.set_current_folder(os.path.dirname(dbpath))
 
         status = f.run()