Add poetry cataloger (#121)

* Minor cleanup

Signed-off-by: Dan Luhring <dan.luhring@anchore.com>

* Update pkg Type definition to string

Signed-off-by: Dan Luhring <dan.luhring@anchore.com>

* Implement poetry.lock parsing

Signed-off-by: Dan Luhring <dan.luhring@anchore.com>

* Address CI issues

Signed-off-by: Dan Luhring <dan.luhring@anchore.com>

* Integrate Alex's changes

Signed-off-by: Dan Luhring <dan.luhring@anchore.com>

syft/cataloger/python/parse_poetry_lock_test.go

@@ -0,0 +1,56 @@
+package python
+
+import (
+	"github.com/anchore/syft/syft/pkg"
+	"github.com/go-test/deep"
+	"os"
+	"testing"
+)
+
+func TestParsePoetryLock(t *testing.T) {
+	expected := []pkg.Package{
+		{
+			Name:     "added-value",
+			Version:  "0.14.2",
+			Language: pkg.Python,
+			Type:     pkg.PoetryPkg,
+			Licenses: nil,
+		},
+		{
+			Name:     "alabaster",
+			Version:  "0.7.12",
+			Language: pkg.Python,
+			Type:     pkg.PoetryPkg,
+			Licenses: nil,
+		},
+		{
+			Name:     "appnope",
+			Version:  "0.1.0",
+			Language: pkg.Python,
+			Type:     pkg.PoetryPkg,
+			Licenses: nil,
+		},
+		{
+			Name:     "asciitree",
+			Version:  "0.3.3",
+			Language: pkg.Python,
+			Type:     pkg.PoetryPkg,
+			Licenses: nil,
+		},
+	}
+
+	fixture, err := os.Open("test-fixtures/poetry/poetry.lock")
+	if err != nil {
+		t.Fatalf("failed to open fixture: %+v", err)
+	}
+
+	actual, err := parsePoetryLock(fixture.Name(), fixture)
+	if err != nil {
+		t.Error(err)
+	}
+
+	differences := deep.Equal(expected, actual)
+	if differences != nil {
+		t.Errorf("returned package list differed from expectation: %+v", differences)
+	}
+}