Make pushsource compatible with attrs version 22.2.0

Since new attrs version release, pub tests have begun failing with the
error "TypeError: keywords must be strings". Attrs have added an "alias"
parameter to each attribute[1], which is used in the attrs's "evolve"
method to construct a new instance. This causes issues with the attribute
"from", which has some special logic implemented in order to be usable
at all[2]. The attribute "from" is generated from "from_", copying all
its parameters. Since "alias" is a new parameter, it isn't copied and
thus its value is set no "None". attrs's "evolve" method uses **kwargs
to create a new instance, and it sets one of the keys in **kwargs to
"None" (from alias). Keys in **kwargs must be strings, which causes the
TypeError. It can be fixed by also setting "alias" in the newly created
"from" attribute. In case of "from_", it has the same value as "name"
parameter ("from_"), which is why we don't want to copy it from the old
attribute, but explicitly set it to "from" (otherwise it would be
"from_"). The change should be backwards compatible with older versions
of attrs.

[1] python-attrs/attrs#950
[2] release-engineering#108

requirements.txt

@@ -4,9 +4,9 @@
 #
 #    pip-compile --generate-hashes requirements.in
 #
-attrs==22.1.0 \
-    --hash=sha256:29adc2665447e5191d0e7c568fde78b21f9672d344281d0c6e1ab085429b22b6 \
-    --hash=sha256:86efa402f67bf2df34f51a335487cf46b1ec130d02b8d39fd248abfd30da551c
+attrs==22.2.0 \
+    --hash=sha256:29e95c7f6778868dbd49170f98f8818f78f3dc5e0e37c0b1f474e3561b240836 \
+    --hash=sha256:c9227bfc2f01993c03f68db37d1d15c9690188323c067c641f1a35ca58185f99
     # via
     #   -r requirements.in
     #   jsonschema
@@ -93,29 +93,34 @@ pushcollector==1.3.0 \
     --hash=sha256:18281fcd4247ca8b668c25348bbc2f9cc032912cecc7037824a74ad8adcbb1c3 \
     --hash=sha256:3b0754dd86e9d66ec1b19f13b66be6582e5d1b5087a1f1db3778485948fc0f28
     # via -r requirements.in
-pyrsistent==0.19.2 \
-    --hash=sha256:055ab45d5911d7cae397dc418808d8802fb95262751872c841c170b0dbf51eed \
-    --hash=sha256:111156137b2e71f3a9936baf27cb322e8024dac3dc54ec7fb9f0bcf3249e68bb \
-    --hash=sha256:187d5730b0507d9285a96fca9716310d572e5464cadd19f22b63a6976254d77a \
-    --hash=sha256:21455e2b16000440e896ab99e8304617151981ed40c29e9507ef1c2e4314ee95 \
-    --hash=sha256:2aede922a488861de0ad00c7630a6e2d57e8023e4be72d9d7147a9fcd2d30712 \
-    --hash=sha256:3ba4134a3ff0fc7ad225b6b457d1309f4698108fb6b35532d015dca8f5abed73 \
-    --hash=sha256:456cb30ca8bff00596519f2c53e42c245c09e1a4543945703acd4312949bfd41 \
-    --hash=sha256:71d332b0320642b3261e9fee47ab9e65872c2bd90260e5d225dabeed93cbd42b \
-    --hash=sha256:879b4c2f4d41585c42df4d7654ddffff1239dc4065bc88b745f0341828b83e78 \
-    --hash=sha256:9cd3e9978d12b5d99cbdc727a3022da0430ad007dacf33d0bf554b96427f33ab \
-    --hash=sha256:a178209e2df710e3f142cbd05313ba0c5ebed0a55d78d9945ac7a4e09d923308 \
-    --hash=sha256:b39725209e06759217d1ac5fcdb510e98670af9e37223985f330b611f62e7425 \
-    --hash=sha256:bfa0351be89c9fcbcb8c9879b826f4353be10f58f8a677efab0c017bf7137ec2 \
-    --hash=sha256:bfd880614c6237243ff53a0539f1cb26987a6dc8ac6e66e0c5a40617296a045e \
-    --hash=sha256:c43bec251bbd10e3cb58ced80609c5c1eb238da9ca78b964aea410fb820d00d6 \
-    --hash=sha256:d690b18ac4b3e3cab73b0b7aa7dbe65978a172ff94970ff98d82f2031f8971c2 \
-    --hash=sha256:d6982b5a0237e1b7d876b60265564648a69b14017f3b5f908c5be2de3f9abb7a \
-    --hash=sha256:dec3eac7549869365fe263831f576c8457f6c833937c68542d08fde73457d291 \
-    --hash=sha256:e371b844cec09d8dc424d940e54bba8f67a03ebea20ff7b7b0d56f526c71d584 \
-    --hash=sha256:e5d8f84d81e3729c3b506657dddfe46e8ba9c330bf1858ee33108f8bb2adb38a \
-    --hash=sha256:ea6b79a02a28550c98b6ca9c35b9f492beaa54d7c5c9e9949555893c8a9234d0 \
-    --hash=sha256:f1258f4e6c42ad0b20f9cfcc3ada5bd6b83374516cd01c0960e3cb75fdca6770
+pyrsistent==0.19.3 \
+    --hash=sha256:016ad1afadf318eb7911baa24b049909f7f3bb2c5b1ed7b6a8f21db21ea3faa8 \
+    --hash=sha256:1a2994773706bbb4995c31a97bc94f1418314923bd1048c6d964837040376440 \
+    --hash=sha256:20460ac0ea439a3e79caa1dbd560344b64ed75e85d8703943e0b66c2a6150e4a \
+    --hash=sha256:3311cb4237a341aa52ab8448c27e3a9931e2ee09561ad150ba94e4cfd3fc888c \
+    --hash=sha256:3a8cb235fa6d3fd7aae6a4f1429bbb1fec1577d978098da1252f0489937786f3 \
+    --hash=sha256:3ab2204234c0ecd8b9368dbd6a53e83c3d4f3cab10ecaf6d0e772f456c442393 \
+    --hash=sha256:42ac0b2f44607eb92ae88609eda931a4f0dfa03038c44c772e07f43e738bcac9 \
+    --hash=sha256:49c32f216c17148695ca0e02a5c521e28a4ee6c5089f97e34fe24163113722da \
+    --hash=sha256:4b774f9288dda8d425adb6544e5903f1fb6c273ab3128a355c6b972b7df39dcf \
+    --hash=sha256:4c18264cb84b5e68e7085a43723f9e4c1fd1d935ab240ce02c0324a8e01ccb64 \
+    --hash=sha256:5a474fb80f5e0d6c9394d8db0fc19e90fa540b82ee52dba7d246a7791712f74a \
+    --hash=sha256:64220c429e42a7150f4bfd280f6f4bb2850f95956bde93c6fda1b70507af6ef3 \
+    --hash=sha256:878433581fc23e906d947a6814336eee031a00e6defba224234169ae3d3d6a98 \
+    --hash=sha256:99abb85579e2165bd8522f0c0138864da97847875ecbd45f3e7e2af569bfc6f2 \
+    --hash=sha256:a2471f3f8693101975b1ff85ffd19bb7ca7dd7c38f8a81701f67d6b4f97b87d8 \
+    --hash=sha256:aeda827381f5e5d65cced3024126529ddc4289d944f75e090572c77ceb19adbf \
+    --hash=sha256:b735e538f74ec31378f5a1e3886a26d2ca6351106b4dfde376a26fc32a044edc \
+    --hash=sha256:c147257a92374fde8498491f53ffa8f4822cd70c0d85037e09028e478cababb7 \
+    --hash=sha256:c4db1bd596fefd66b296a3d5d943c94f4fac5bcd13e99bffe2ba6a759d959a28 \
+    --hash=sha256:c74bed51f9b41c48366a286395c67f4e894374306b197e62810e0fdaf2364da2 \
+    --hash=sha256:c9bb60a40a0ab9aba40a59f68214eed5a29c6274c83b2cc206a359c4a89fa41b \
+    --hash=sha256:cc5d149f31706762c1f8bda2e8c4f8fead6e80312e3692619a75301d3dbb819a \
+    --hash=sha256:ccf0d6bd208f8111179f0c26fdf84ed7c3891982f2edaeae7422575f47e66b64 \
+    --hash=sha256:e42296a09e83028b3476f7073fcb69ffebac0e66dbbfd1bd847d61f74db30f19 \
+    --hash=sha256:e8f2b814a3dc6225964fa03d8582c6e0b6650d68a232df41e3cc1b66a5d2f8d1 \
+    --hash=sha256:f0774bf48631f3a20471dd7c5989657b639fd2d285b861237ea9e82c36a415a9 \
+    --hash=sha256:f0e7c4b2f77593871e918be000b96c8107da48444d57005b6a6bc61fb4331b2c
     # via jsonschema
 python-dateutil==2.8.2 \
     --hash=sha256:0123cacc1627ae19ddf3c27a5de5bd67ee4586fbdd6440d9748f8abb483d3e86 \

src/pushsource/_impl/model/erratum_fixup.py

@@ -53,6 +53,8 @@ def __init__(self, delegate, attrs_old_to_new):
             # (we do this dynamically to cope with differences between ancient and newer
             # versions of attrs library)
             attr_kwargs = {"name": new_name}
+            if hasattr(old_attr, "alias"):
+                attr_kwargs["alias"] = new_name
             for argname in [
                 "default",
                 "validator",