more robust parsing of dpcolor to a semver (#254)

cmd/provision/proxies/remote-service-gcp/apiproxy/resources/py/get-runtime-version.py

@@ -12,12 +12,33 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+"""
+Set the "runtime_version" flow variable to a semver-style version made
+by splitting APIGEE_DPCOLOR by "-" and concatenating the first three
+segments that are digits. If this fails, the var is set to "unknown."
+"""
+
 import os
 
-version = os.environ.get("APIGEE_DPCOLOR", "")
 
-if len(version) > 0:
-    dig = [c for c in version if c.isdigit()]
-    flow.setVariable("runtime_version", ".".join(dig[0:3]))
-else:
-    flow.setVariable("runtime_version", "unknown")
+def make_semver(version_string):
+    if not version_string:
+        return "unknown"
+
+    nums = []
+    for segment in version_string.split("-"):
+        try:
+            int(segment)
+            nums.append(segment)
+        except ValueError:
+            pass
+
+    if len(nums) < 3:
+        return "unknown"
+
+    return ".".join(nums[:3])
+
+
+dp_color = os.environ.get("APIGEE_DPCOLOR", "")
+semver = make_semver(dp_color)
+flow.setVariable("runtime_version", semver)