uhd_images_downloader: Add environment variable for http auth

This allows the image downloader to download files from restricted sources
using HTTP basic auth, specifying the credentials in the UHD_IMAGES_USER and
UHD_IMAGES_PASSWORD environment variables:
```
UHD_IMAGES_USER=lane UHD_IMAGES_PASSWORD=MyS3cretPassword uhd_images_downloader.py
```

2 files changed, 46 insertions, 0 deletions

diff --git a/host/tests/CMakeLists.txt b/host/tests/CMakeLists.txt
index 19d6bd23c..99f4e5eaf 100644
--- a/host/tests/CMakeLists.txt
+++ b/host/tests/CMakeLists.txt
@@ -72,6 +72,7 @@ set(pytest_sources
     pyranges_test.py
     verify_fbs_test.py
     pychdr_parse_test.py
+    uhd_image_downloader_test.py
 )
 
 #turn each test cpp file into an executable with an int main() function
diff --git a/host/tests/uhd_image_downloader_test.py b/host/tests/uhd_image_downloader_test.py
new file mode 100644
index 000000000..ef5c0b5a3
--- /dev/null
+++ b/host/tests/uhd_image_downloader_test.py
@@ -0,0 +1,45 @@
+#
+# Copyright 2020 Ettus Research, a National Instruments Brand
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+Unit test for uhd_images_downloader
+"""
+
+import unittest
+import uhd_images_downloader
+
+def mk_env(username, password):
+    env = {}
+    if username is not None:
+        env[uhd_images_downloader._USERNAME_VARIABLE] = username
+    if password is not None:
+        env[uhd_images_downloader._PASSWORD_VARIABLE] = password
+    return env
+
+class PyImageDownloaderTest(unittest.TestCase):
+    """ Test Python image downloader functionality """
+    def test_parse_auth_works(self):
+        self.assertEqual(
+            uhd_images_downloader.parse_auth(mk_env("bbrother", "2+2=5")),
+            ("bbrother", "2+2=5")
+        )
+
+    def test_parse_auth_empty_on_empty(self):
+        self.assertEqual(
+            uhd_images_downloader.parse_auth(mk_env(None, None)),
+            None
+        )
+        self.assertEqual(
+            uhd_images_downloader.parse_auth(mk_env("", None)),
+            None
+        )
+
+    def test_throws_on_empty_pw(self):
+        with self.assertRaises(RuntimeError):
+            uhd_images_downloader.parse_auth(mk_env("username", None))
+
+    def test_throws_on_empty_username(self):
+        with self.assertRaises(RuntimeError):
+            uhd_images_downloader.parse_auth(mk_env(None, "password"))