Add environment auth option

Author: eculler

earthpy/appeears.py

@@ -12,11 +12,11 @@
 import os
 import pathlib
 import re
-import requests
 import time
 from glob import glob
 
 import keyring
+import requests
 
 class AppeearsDownloader(object):
 	"""
@@ -174,6 +174,14 @@ def login(self, service='NASA_EARTHDATA', username_id='NED_USERNAME'):
 		except:
 			username = None
 			password = None
+			
+		# Get username and password from environment
+		try:
+			username = os.environ['EARTHDATA_USERNAME']
+			password = os.environ['EARTHDATA_PASSWORD']
+		except:
+			username = None
+			password = None
 
 		# Prompt user if no username or password is stored
 		if (username is None) or (password is None):
@@ -337,4 +345,4 @@ def download_files(self, cache=True):
 						f.write(data)
 
 		# Remove task id file when download is complete
-		os.remove(self.task_id_path)
+		os.remove(self.task_id_path)