Handle the correct exception when formatting extremely high amounts of bytes

Found in production. Yes really. Due to some borked LXC integration, my
snikket host reports

```
MemTotal:       9007199254740991 kB
MemFree:        9007199254690591 kB
MemAvailable:   9007199254690591 kB
```

That is more than 1024 TiB, so it tries to go further up in the scale,
which then causes a Guru Meditation because of the uncaught IndexError.

Dockerfile

@@ -1,7 +1,13 @@
-FROM debian:buster-slim
+FROM debian:bullseye-slim AS build
 
-ARG BUILD_SERIES=dev
+RUN set -eu; \
-ARG BUILD_ID=0
+    export DEBIAN_FRONTEND=noninteractive ; \
+    apt-get update ; \
+    apt-get install -y --no-install-recommends \
+        python3 python3-pip python3-setuptools python3-wheel \
+        libpython3-dev \
+        make build-essential \
+        netcat;
 
 COPY requirements.txt /opt/snikket-web-portal/requirements.txt
 COPY build-requirements.txt /opt/snikket-web-portal/build-requirements.txt
@@ -11,32 +17,41 @@ COPY babel.cfg /opt/snikket-web-portal/babel.cfg
 
 WORKDIR /opt/snikket-web-portal
 
-RUN set -eu; \
+RUN pip3 install -r requirements.txt; \
-    export DEBIAN_FRONTEND=noninteractive ; \
-    apt-get update ; \
-    apt-get install -y --no-install-recommends \
-        python3 python3-pip python3-setuptools python3-wheel \
-        libpython3-dev \
-        make build-essential \
-        netcat \
-        ; \
-    pip3 install -r requirements.txt; \
     pip3 install -r build-requirements.txt; \
-    make; \
+    make;
-    pip3 uninstall -yr build-requirements.txt; \
+
-    apt-get remove -y build-essential make libpython3-dev; \
+
-    apt-get autoremove -y; \
+FROM debian:bullseye-slim
-    pip3 install hypercorn; \
+
-    rm -rf /root/.cache; \
+ARG BUILD_SERIES=dev
-    apt-get clean ; rm -rf /var/lib/apt/lists
+ARG BUILD_ID=0
 
 COPY docker/env.py /etc/snikket-web-portal/env.py
+
 ENV SNIKKET_WEB_PYENV=/etc/snikket-web-portal/env.py
 
 ENV SNIKKET_WEB_PROSODY_ENDPOINT=http://127.0.0.1:5280/
 
 HEALTHCHECK CMD nc -zv ${SNIKKET_TWEAK_PORTAL_INTERNAL_HTTP_INTERFACE:-127.0.0.1} ${SNIKKET_TWEAK_PORTAL_INTERNAL_HTTP_PORT:-5765}
 
+RUN set -eu; \
+    export DEBIAN_FRONTEND=noninteractive ; \
+    apt-get update ; \
+    apt-get install -y --no-install-recommends \
+        python3 python3-pip python3-setuptools python3-wheel; \
+    apt-get clean ; rm -rf /var/lib/apt/lists; \
+    pip3 install hypercorn; \
+    rm -rf /root/.cache;
+
+WORKDIR /opt/snikket-web-portal
+
+COPY requirements.txt /opt/snikket-web-portal/requirements.txt
+RUN pip3 install -r requirements.txt; rm -rf /root/.cache;
+
+COPY --from=build /opt/snikket-web-portal/snikket_web/ /opt/snikket-web-portal/snikket_web
+COPY babel.cfg /opt/snikket-web-portal/babel.cfg
+
 RUN echo "$BUILD_SERIES $BUILD_ID" > /opt/snikket-web-portal/.app_version
 
 ADD docker/entrypoint.sh /entrypoint.sh

snikket_web/infra.py

@@ -53,11 +53,14 @@ def circle_name(c: typing.Any) -> str:
 
 
 def format_bytes(n: float) -> str:
-    scale = math.floor(math.log(n, 1024))
+    try:
+        scale = max(math.floor(math.log(n, 1024)), 0)
+    except ValueError:
+        scale = 0
     try:
         unit = BYTE_UNIT_SCALE_MAP[scale]
         factor = 1024**scale
-    except ValueError:
+    except IndexError:
         unit = "TiB"
         factor = 1024**4
     if factor > 1:

snikket_web/xmpputil.py

@@ -207,7 +207,7 @@ def make_avatar_metadata_set_request(
         item,
         "metadata", xmlns=NS_USER_AVATAR_METADATA)
 
-    attr: typing.MutableMapping[str, str] = {
+    attr: typing.Dict[str, str] = {
         "id": id_,
         "bytes": str(size),
         "type": mimetype,
@@ -217,7 +217,12 @@ def make_avatar_metadata_set_request(
     if height is not None:
         attr["height"] = str(height)
 
-    ET.SubElement(metadata_wrap, "info", xmlns=NS_USER_AVATAR_METADATA, **attr)
+    ET.SubElement(
+        metadata_wrap,
+        "info",
+        xmlns=NS_USER_AVATAR_METADATA,
+        **attr,  # type: ignore
+    )
     return req