fixup: fix update-server tests on windows

same colorama problem we saw a while ago from pytest-dev/pytest#3434

Author: sfoster1

update-server/Pipfile

@@ -22,6 +22,7 @@ sphinx = "==1.4.8"
 twine = "==1.12.1"
 wheel = "==0.30.0"
 coverage = "==4.4.2"
+colorama = "*"
 
 
 [requires]

update-server/Pipfile.lock

@@ -61,8 +61,11 @@ def extracted_update_file(request, tmpdir):
     if request.node.get_marker('bad_hash'):
         hashval = b'0oas0ajcs0asd0asjc0ans0d9ajsd0ian0s9djas'
     else:
-        shasum_out = subprocess.check_output(
-            ['shasum', '-a', '256', rootfs_path])
+        try:
+            shasum_out = subprocess.check_output(
+                ['shasum', '-a', '256', rootfs_path])
+        except subprocess.CalledProcessError:
+            pytest.skip("no shasum invokeable on command line")
         hashval = re.match(b'^([a-z0-9]+) ', shasum_out).group(1)
     with open(hash_path, 'wb') as rfsh:
         rfsh.write(hashval)