Bring in the latest pub_semver

Change-Id: Ibd772c70d596fdc32c6654a058bf44ef0ab787a0
Reviewed-on: https://dart-review.googlesource.com/49827
Commit-Queue: Natalie Weizenbaum <nweiz@google.com>
Reviewed-by: Bob Nystrom <rnystrom@google.com>

Author: nex3

CHANGELOG.md

@@ -25,6 +25,17 @@
 
 #### Pub
 
+* Fix a bug where the version solver could loop infinitely when resolving a
+  conflict involving pre-release constraints ([issue 1863][pub#1863]).
+
+[pub#1863]: https://github.com/dart-lang/pub/issues/1863
+
+## 2.0.0-dev.45.0
+
+### Tool Changes
+
+#### Pub
+
 * Fix a bug where the version solver could crash when resolving a conflict
   involving pre-release constraints ([issue 1856][pub#1856]).
 

DEPS

@@ -116,7 +116,7 @@ vars = {
   "pool_tag": "@1.3.4",
   "protobuf_tag": "@0.7.1",
   "pub_rev": "@4947e0b3cb3ec77e4e8fe0d3141ce4dc60f43256",
-  "pub_semver_tag": "@1.3.4",
+  "pub_semver_tag": "@1.3.6",
   "quiver_tag": "@5aaa3f58c48608af5b027444d561270b53f15dbf",
   "resource_rev":"@af5a5bf65511943398146cf146e466e5f0b95cb9",
   "root_certificates_rev": "@16ef64be64c7dfdff2b9f4b910726e635ccc519e",