Fixed set operation from undefined += to a union (#1963)

Fixed flake8 issues

Fixed set operation from undefined += to a union (#1963)
bd61a365 · James Wynne III · Todd Gamblin · b7a612dc · bd61a365
Commit bd61a365 authored 8 years ago by James Wynne III Committed by Todd Gamblin 8 years ago
--- a/lib/spack/spack/provider_index.py
+++ b/lib/spack/spack/provider_index.py
@@ -232,7 +232,8 @@ def merge(self, other):
                    spdict[provided_spec] = opdict[provided_spec]
                    continue

-                spdict[provided_spec] += opdict[provided_spec]
+                spdict[provided_spec] = \
+                    spdict[provided_spec].union(opdict[provided_spec])

    def remove_provider(self, pkg_name):
        """Remove a provider from the ProviderIndex."""