Bump github.com/pkg/errors from 0.8.1 to 0.9.1

Bumps [github.com/pkg/errors](https://github.com/pkg/errors) from 0.8.1 to 0.9.1.
- [Release notes](https://github.com/pkg/errors/releases)
- [Commits](pkg/errors@v0.8.1...v0.9.1)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

go.mod

@@ -24,7 +24,7 @@ require (
 	github.com/opencontainers/go-digest v1.0.0-rc1
 	github.com/opencontainers/image-spec v1.0.2-0.20190823105129-775207bd45b6
 	github.com/pierrec/lz4 v2.4.0+incompatible // indirect
-	github.com/pkg/errors v0.8.1
+	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.4.0
 	github.com/urfave/cli v1.22.2
 	github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8 // indirect

go.sum

@@ -184,6 +184,8 @@ github.com/pierrec/lz4 v2.4.0+incompatible/go.mod h1:pdkljMzZIN41W+lC3N2tnIh5sFi
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/pquerna/ffjson v0.0.0-20181028064349-e517b90714f7 h1:gGBSHPOU7g8YjTbhwn+lvFm2VDEhhA+PwDIlstkgSxE=